مجله مهندسی مکانیک
سال پنجاهم شماره 3 (پیاپی 92، پاییز 1399)

Todays, structural analysis techniques have been improved, and structural engineers are able to build High-Rise Buildings. In these structures, it should be noted that elevation is often accompanied by an increase in the softness, which increases the sensitivity of the structure to dynamic forces such as wind. The purpose of the present study is to study the wind-induced vibrations on tall buildings, taking into account the effects of vortices created by the fluid flow and also the controlling this phenomena. To this end, the governing equations of the structure, the fluid flow and the tuned-mass damper are first introduced, and their coefficient values are extracted according to the characteristics of ACT skyscraper and solved using a program coded in MATLAB. After validating the results, the effects of wind loads are investigated by considering vortex effects as well as different wind velocity profiles; and the results are compared with the case where no vortices are considered and the optimal operating range of TMD is defined. At last, parametric study on mass ratio and wind speeds are presented.

Fitness for Service (FFS) methodology assessment of defective pipes and pressure vessels in oil and gas industries is offered in API-579 standard. The defective pipes operation are allowed just if they have been evaluated based on FFS method and their operating pressure has been confirmed whether the defects caused by cracks or different corrosion types. Through the current study FFS evaluation procedure was benefited to find the safe operating pressure for a 16 inches defective pipe consisting a local metal loss defect (Max. depth of 8mm) with an internal pressure of 33 MPa. Furthermore, the time needed for the next FFS examination had been presented. The analyzed pipe was about 4 years in service and is located in an injection line of a natural gas reservoir. The required experimental data related to the thickness of this pipe were collected using phased array ultrasonic test on the operating site. The results indicated that the defective pipe could operate well in service for next two years without any demands for repair or replacement.

One of the methods to improve the performance of diesel engine is the upgrade in the injection features and adopting some schemes in order to create a more homogenous and uniform mixture of the sprayed fuel with accessible air within combustion chamber. As to form a desirable condition conducive to stoichiometric mixture, factors such as the injection timing and air swirl ratio in combination were analyzed in this project and the optimum solution leading to maximum combustion and minimum emissions were introduced. The obtained numerical results by AVL FIRE for the base case have been compared with experimental ones showing a good agreement and indicative of reliability to modeling procedure. According to obtained results, the advanced injection mode of 712 CA results in greater uniformity index and the effect of swirl ratio is more sensible on ERUI at advanced injections rather than retarded injections. From the pollutant emissions aspect, the late injection policies are recommended since it is capable of simultaneous reduction of soot and NOx. In general, the compound cases of 712 CA- 1200 1/min and 723 CA- 1500 1/min are ideal for combustion and emission control strategies, respectively. The results can be programmed for electronic injection regulation through ECU system of engines while an appropriate swirl amount applied to achieve the results of interest.

One of the most important challenges faced by pharmacists is the inability to produce drug carriers with precision and control in a specific number. Therefore, droplet production with the aid of microfluidic devices as adaptive devices with the wide range of application is used. The purpose of this research is producing droplets as a structure for drug carrier with the aid of microfluidic devices with flow-focusing geometry. Also, the effect of geometrical, mechanical and fluid characteristics on the diameter of the produced droplets (Using two types of oily paraffin and hexadecane separately as continuous fluid and water as a discrete fluid) has been evaluated, empirically. As a results, by increasing the angle between the main and secondary channels and increasing the width of the channels, the diameter of the droplets expanded exponentially and relatively linearly, respectively. However, by decreasing the viscosity ratio to the surface tension of the fluid, the diameter of the produced droplets decreases relatively linearly. Moreover, in all studies, when the regimen changes, the mutation of the microchip occurs, In addition, the flow rate of continuous phase increases and the diameter of the produced droplets decreases.

Centrifugal pumps are widely used in various industries, specially the oil industry. Therefore, investigation of the pattern of flow in the pump and flow behavior arisen from pump geometric variations to optimize design, is of great importance. In this paper, 3D flow in E.S.P. pump which is a centrifugal down hole submersible pump is numerically simulated and the effect of diameter and number of blades of impeller are assessed. Multiple reference frame method is used to model of relative motion of impeller and diffuser and frozen rotor interface is utilized to connect them. The results show that pump head is increased and efficiency is reduced with increase in impeller diameter .Reducing the diameter has a reverse effect. The variations arisen from increase and decrease in diameter are because of the variation in outlet flow angle and increase in frictional losses, respectively. Also, results show that increase in the number of impeller blades cause to increase in head and decrease in efficiency. These variations have happened due to the increased levels of energy transfer to the fluid, as well as increased frictional losses.

This paper presents a new approach to design a controller for nonlinear systems using the iterative approximation method. In the proposed approach, the nonlinear system is first approximated by several linear time-varying systems. Then, for each of the linear systems, a control law is designed and the calculated control law for the last system is applied to the nonlinear system. This paper shows that the conventional method in the iterative approximations is practically open-loop and becomes unstable after a short time. Then, the maximum duration of the stability in conventional controllers called T is evaluated using simulations in the case of a robot arm. In this paper, to establish a relationship between the controller and the nonlinear system, the process of approximation and design of the controller is repeated every T seconds. In this way, the control system is closed-loop, and every T second, using the updated feedback signal form the nonlinear system the control signal is updated. Finally, the efficiency of the proposed method is shown through a simulation.

In this paper, numerical simulation of the convection heat transfer in micro-channel heat sinks is investigated. The main objective of this research is to study the effect of diameter, distance between fins and fins height, as well as the inlet fluid velocity on the average temperature fins, average temperature of fluid at outlet, temperature distribution in longitudinal direction of the micro-channel and heat flux passing fins. For this purpose, the cooling fluid flow passing through a micro-channel heat sinks with bar fins which have the elliptical cross-section and placed in a linear arrangement is simulated using a finite volume method. Simulation results indicate that changes in diameter and distance between the fins as well as the velocity of the inlet fluid have a significant effect on the heat transfer rate of the heat sink, but the temperature variations due to the change in the height of the fins are low.

In this paper, the pressure and temperature distributions over the ramp of an Aerospike nozzle in different pressure ratios are presented. Governing equations of the turbulent flow have been solved using the finite volume method and different turbulence models. By comparing the obtained results with available experimental data, SST k-ω model has been selected for numerical simulations. In this study, the length of the recirculation zone, the temperature, and pressure variations within the recirculation zone and locations of the separation and reattachment points have been investigated in detail. Results show that the increase in the pressure ratio can move separation, reattachment points, and recirculation zone to downstream of the flow and also increase the length of the recirculation zone simultaneously. The maximum and minimum temperatures did not change but the maximum and minimum pressures reduced. Also, the results show that the reattachment point has the maximum temperature of the flow and this maximum temperature point can be adopted as the reattachment point.

The most important factor that threatens the health of a structure is the existence of imperfections that occur or appear in different contexts as damage. Therefore it is necessary to have adequate cognition of the effect of the presence of different types of damage on the mechanical response of the structure. In the present paper, the effect of the presence and characteristics of damage on the light aircraft wing composite spar as one of the most important components from the perspective of computing the variations of its mechanical response in the criterion points has been investigated.By determining the effects, the algorithm of the implementation of the health monitoring system of the structure will be identifiable. The computation and observation of changes in the mechanical properties of spar in a variety of models have been performed as the basis of the composite spar health monitoring process through FEM. The results represents that the mechanical behavior of composite spar in different loadings are in direct relation with the location of damage in which nucleated, damage growth process and sizes. The damage location represents more important effect than the damage size to the changes produced in the mechanical behavior of the composite spar.

This paper is concerned with the controller design for formation of a group of non-holonomic mobile robots based on distributed suboptimal method in the presence of environmental obstacles. Formation control of mobile robots is one of the important aspects in group movement and cooperative behavior of multi-agent systems. Challenges and constraints on procedure mechanisms and unknown dynamic environments have made the control process of such systems more complicated. In this study, integrated leader-follower method and behavioral approach also for each of the desired behaviors including geometrical formation, trajectory tracking and obstacle collision avoidance, a cost function and a formation error dynamic equation are defined as constraints. The main goal in the present paper is to design an optimum control law for the robots applicable to the whole constraints and limits of the problem while minimizing certain criterion. The present research study also presents a stability analysis to show the closed loop system is stable and works optimally. The simulation results illustrate the effectiveness and efficient performance of the proposed suboptimal control law design.

In this paper, the effect of using various intelligent algorithms to optimize the adaptive neuro-fuzzy disturbance observer has been investigated .First, a model reference adaptive control is designed for the spacecraft simulator. Then, in order to reduce the disturbance effect, an adaptive neuro-fuzzy disturbance observer is used. In this paper, the fuzzy system is optimized using Intelligent Genetic Algorithm, Particle Swarm Optimization, Imperialist Competitive Algorithm, Bee Colony, Ant Colony Optimization, and especially Policy Gradient Particle Swarm Algorithm, which speeds up and optimizes the response. The Policy Gradient Particle Swarm algorithm is a combination of gradient policy reinforcement learning and particle swarming ideas and is a hybrid optimization method to control a nonlinear complex system with many applications in the real world. In this method, influenced by reinforcement idea, the policy gradient for a non-fossilized system is calculated, and in the optimization of particle swarm relations, optimization is performed in addition to the factors included in the congestion methods in the direction of the policy gradient. It is intended to optimize the fuzzy neuro system parameters and input and output data in the cost function. Finally, the neuro-fuzzy systems optimized by these algorithms are compared and it is shown that the gradient particle swarm algorithm performs better than the particle swarm algorithm.

In this paper, a novel algorithm for the real-time modeling of the inertial sensor errors is developed based on the genetic algorithm. In the inertial navigation systems, failure to compensate inertial sensor errors not only could result in exponentially increasing of positioning errors, but also leads to loss of precision in the estimation of other states. This subject indicates the importance of providing an accurate algorithm for sensor errors modeling in the Inertial Navigation Systems (INS). In this respect, a genetic algorithm is proposed in this study for modeling of inertial sensor errors. The main aim of designing this algorithm is to improve the estimation accuracy of position, velocity and attitude of the INS in the presence of uncertainties in inertial sensors. Some vehicular tests have been carried out in order to comparison, implementation and verification of the proposed integration scheme. The experimental results indicate that the proposed algorithm enhanced the estimation accuracy compared with the conventional Gauss-Markov model. Therefore, in general, the proposed method will improve the results of inertial navigation.

In this research, the microstructure and mechanical properties of AISI310 austenitic stainless steel/API5LX60 low alloy steel dissimilar joints welded in three different heat inputs, were studied. Gas tungsten arc welding (GTAW) Process and ER2209 filler metal was used for preparing the joints. After welding, the microstructure of different regions of each joint, including base metal, weld metal, heat affected zone (HAZ) and the interface were investigated using optical microscope. Studying fracture surface of the weldments prepared in different heat inputs was performed using scanning electron microscope (SEM). Mechanical properties of the joints were evaluated using impact and micro-hardness tests. Microstructural studies showed that using ER2209 filler metal has led to a ferritic-austenitic microstructure at the weld metal. It was found by increasing the heat input, no significant microstructural change occured at the heat affected zone of AISI310 steel, but the change in microstructure at the heat affected zone of API5LX60 steel was clearly visible. The results of impact tests showed a considerable increase in fracture energy of the weld metal by increasing the heat input. In addition increase in the heat input, has not a noticeable effect on the weld metal hardness, and change in hardness of the weld metal due to increasing the heat input was quite low and negligible.

Due to various benefits of composite materials such as light weight, high strength and their excellent formability, the external bonded composite patches have been proved to be a preferable method of repairing flaws and cracks in various engineering structures. In this paper, the effect of some parameters such as the composite patch material, the adhesive material and the base plate material on the reduction of the stress intensity factor and the variation of fracture initiation angle has been studied using the 3D finite element method. The results showed that the composite patch material and base plate material have significant effect on reduction of stress intensity factor. However, the adhesive material has insignificant effect on it. One of the other important results of this study is that the use of patch does not have a significant impact on the fracture initiation angle.

Determination of temprature distribution is a critical factor in thermal treatment of diseased organs such as cancerous tumors. In this paper is, the optimal power of the heat source is estimated in order to destroy cancer cells due to the temperature distribution in the cancerous tissue. The geometry of breast is represented as a hemisphere containing three layers, muscle, gland and fat. The conjugate gradient method is used to solve the inverse
heat conduction problem using Pennes bioheat equation in the axisymmetric coordinate system.To make the solve of the problem easier, the irregular region
in the physical domain (r,z ) is transformed into a rectangle
in the computational domain (ξ , η).

Due to the widespread use of unstiffened and stiffened composite shells in different industries, investigating their vibrational behavior has great importance. In this paper, the effects of different parameters on the vibration of these shells are studied using experimental and numerical analysis. Specimens used for modal analysis are fabricated by filament winding machine. The mechanical properties of fibers and resin matrix are determined based on the standard tests as the fiber volume fraction in the shell and the stiffeners. Finally, the mechanical properties are calculated using micromechanical relations. These properties are used for finite element modeling by ABAQUS package. FE results are validated in comparison with empirical tests. Finally, the effects of different parameters on the vibrational behavior of composite shells are studied using this FE model. The results show that using the stiffeners does not necessarily increase the natural frequencies of the shell. From the vibrational point of view, the results of the stiffened shell with circumferential rings, kagome grid, and triangle grid are similar. So, considering the manufacturing procedure, stiffening the shell with circumferential rings is preferred.

In this research, it is tried to study fuel cell turbo-expander hybrid system for gas pressure reduction stations. This research is based on thermodynamic equations for the behavior of hybrid systems in various conditions. Gas pressure reducing stations reduce gas pressure from 5000 kPa to around 1000 kPa. This pressure reduction is performed by expansion a valve that does not produce any energy. Electricity can be produced and injected to the grid by adding a turbo-expander and fuel cell in a gas reducing station. In winter, due to low temperature and high pressure of inlet gas, gas freezing can causes damage in turbo-expander and expansion valve, for this reason a boiler is used in cold months to produce heat for increasing the inlet gas temperature. Since fuel cell can generate considerable heat during its operation, it can be used for preheating the inlet gas and lower the fuel consumption. The results show that pressure reduction station which consisted of a fuel cell and a turbine has 5 to 10% more efficiency than a pressure reducing station which consisted of a fuel cell and expansion valves; however the amount of fuel consumption is equal for both systems. For pressure reduction station with fuel cell, the fuel consumption is very higher than the pressure reduction station without fuel cell; because more fuel will be consumed for electricity. The results show that more efficiency can be obtained by using the fuel cell in pressure reducing station and thus fuel consumption will be more reduced compared with a combined cycle power plant

Using high-performance thermodynamic cycles to generate power from existing heat sources is an effective strategy for sustainable energy development. In this study, a new integrated cycle (triple flash and single flash combined cycle with Organic Rankine cycle) based on different real temperatures and pressures in Sabalan geothermal power plant is proposed and analyzed from thermodynamic and exergy viewpoint. A comprehensive parametric study is performed by EES software and then, the proposed cycle is optimized for four considered working fluids relative to the flash chambers’ pressure (or valve 1, 2 and 3 pressures), the evaporator temperature, and the pinch point temperature difference of evaporator. The results show that isobutane is the most suitable fluid for the Rankine cycle. The power generation, thermal and exergy efficiency, in this case for optimum condition, was calculated to be 23073 kW, 19/73%, and 75.67%, respectively. In optimum condition and compared to other studies which has similar wellhead for Sabalan geothermal power plant, the proposed cycle had better performance from energy and exergy viewpoints.

In the present study, the fluid flow and heat transfer of water-AL2O3 nanofluid through a three-dimensional microcooler with rectangular flow passages are investigated numerically in the presence of a uniform magnetic field. The magnetic field is applied in the transverse direction (i.e. normal to the flow direction). All simulations are performed for Hartman numbers within the range of 0 to 30 for a fixed Reynolds number of Re=100 and the volume fraction of Ø=0.02. The results are presented in terms of the Poiseuille number (f.ReDh), the dimensionless maximum axial velocity (Umax), and the Nusselt number (Nu) as well as contours of velocity and temperature fields. The results reveal that the pressure drop and heat transfer increase with the increase of the Hartman number. In addition to having a uniform temperature distribution in the fluid part, the presence of the magnetic field makes the temperature distribution within the solid part of the micro-channel more uniform which enables removing higher heat fluxes within the safe temperature limit.

In this paper, entropy generation of Al2O3-water nanofluid in a solar flat plate collector with twisted tapes has been investigated numerically. ANSYS Fluent commercial software has been used for numerical simulation. Realizable k-ε turbulence model was applied for turbulent flow modeling. The analysis of entropy generation can help to best design from theory of the second law of thermodynamics. Influences of arrangements of the twisted tape and Reynolds number on frictional and thermal entropy generations have been presented. By increasing the diameter ratio (D* ) and revaluation of ratio (N), the heat transfer rate is increased. So, the thermal entropy generation is reduced with rise of such parameters but opposite trend is observed for friction entropy generation due to the increase of the velocity gradient. The smallest values of thermal and frictional entropy generations rate are obtained 4748.13 W/m3K and 17.33 W/m3K, respectively. Moreover, Bejan number decreases with increase of D * , N and Re. The best design belongs to the case with highest second law efficiency (about 68%) which is occurred for greatest diameter ratio, revaluation of ratio and Reynolds number.

In this research, a standard propeller was designed for a surface vessel, then using a computer program, 3D propeller geometry based on two- dimensional data generated and griding and flow field around the propeller was solved based on the computational fluid dynamics method. In this regard, we used a hybrid grid and periodic condition based on a spline Cutting. A steady model and three unsteady models were used in the numerical modeling. The results were validated and uncertainty grid discretization error was calculated. The results were in good agreement with the results of open water, an estimated separation point and propeller wake were investigated. In order to modeling the transition of the boundary layer, two models of gamma and γ-Reθ transition were used. The Q criterion was used to detection vortices and wakes. The separation of flow and transition of the boundary layer from laminar to turbulent in high advanced coefficients in the unsteady models was different of the steady model. The effects of adding two standard duct with 19A and 37A with open propeller were compared that 19A duct had better hydrodynamic properties.

Nowadays solar still is widely used in solar desalination processes. This work presents a modified stepped solar still with 7 steps 35 mm high, 80 mm wide and 600 mm long and external condenser. Phase Change Material is used as a heat storage source to continue to sweeten saline water after sunset. In this study, stearic acid has been used as phase change material. In order to increase the efficiency of the still, a fan has been used to suck the air in the stepped solar still and transfer it to the condenser. The experiment was carried out in four modes: the first mode was simple, the second mode was only with the fan and the condenser, the third mode, with stearic acid as phase change material, and the fourth mode was used simultaneously with the PCM and external condenser. The results show that the maximum productivity was obtained in fourth mode of experiment which is increased 104%.

Inlet in ramjet engines are used to reduce the air flow from free stream to the required speed for flame stability in the combustion chamber. Hence the precise and correct design of inlet have rightly influence on whole system of ramjet engine performance. At the present work, an axisymmetric supersonic inlet with external compression has been designed based on requirements of the ramjet engine at Mach 2.1. Steady flow simulation was done for inlet individually by CFD software in different fuel flow and Mach numbers to investigate the inlet performance that integrated by other parts of engine. Then transient simulation performed for integrated engine by selection of a special fuel flow-time function that injected in combustor. The results of simulation exhibited the shock velocity and performance of inlet that integrated by the engine. The results show that the designed geometry can meet the desired performance requirements considering the fuel control system ability.

The purpose of this research is to study the amount of energy consumed by the residential building and attempts to optimize it. In this work, the heating and cooling load of a residential tower in a hot and dry climate in Tehran has been calculated by Carrier software. To optimize energy consumption, changes in the material and color of the exterior walls and the change of the window's type and also the examination of the presence of shades to reduce the heat transfer coefficient were made. Results indicate that the change in the type of window will reduce the thermal and cooling load significantly. By replacing the single-layer window with the double-layer reflex one, the thermal load required to provide comfort conditions in the building in the winter is reduced by about 40%. The shading on the windows and also the change in the color of the external walls have each about 3 percentages reducing effect on the thermal and cooling load of the building, that is of less importance in comparison with the effect of windows type. Also choosing optimized materials for external walls leads to about 9 % load reduction in the winter and 6% in the summer. Finally, by calculating optimization process cost and also the cost of consuming energy for the building heating and cooling, the Break-even point and the return cost time regarding to the changes in the material of the window and the exterior wall were investigated. In the best situation the return cost time is about 3 years.

In this paper, the heat transfer characteristics of a cam-shaped tube with aspect ratios from L/D=1.35 to 3.74 in the crossflow of air have been experimentally investigated for two angles of attack, 0o and 180o. The Reynolds number varies in the range of 20000 to 46000 based on the equivalent diameter of a circular tube. One can conclude from the results that the best thermal performance was for L/D=1.35 at 180 degrees. The mean Nusselt number for this tube is 11% higher than that of a circular tube with equivalent diameter. For this tube, when the Reynolds number is 20695, the mean Nusselt number is 19.4% higher than that of a circular tube with equivalent diameter. And the lowest mean Nusselt number was recorded for the tube with L/D=3.74 at zero angle of attack. The mean Nusselt number for this tube is 21% lower than that of a circular tube with equivalent diameter.

Nowadays importance of thrusters in movement of space bodies is not obscure. This article is devoted to study and compare two 5 newton lab-scale thrusters Hydrogen peroxide and Nitrous oxide using uncertainty analysis in order to select the more exact and desirable one in case of produced thrust. The data are extracted from experiments tested in aerospace research-center lab. Hydrogen peroxide thruster specifications are 85% of sincerity, 0.15 bar pressure drop in injector, 150 units of catalyst activity, 0.05 bar ambient pressure and 0.01 amount of feed load. On the other hand specifications of Nitrous oxide thruster are 7.36 gr/s mass flow rate, 2.017 mm diameter of throat. Based on calculations, total uncertainty and relative uncertainty for hydrogen peroxide thruster obtained respectively 0.53, 0.73(or14.68%). These amounts for nitrous oxide thruster obtained respectively 0.52, 0.53(or10.27%). Finally the results show that application of nitrous oxide thruster in terms of accuracy, is more desirable and the amount of it’s produced thrust is closer to the amount of five newton desirable thrust.

In this research, the effect of the number of fins and contribution of walls with and without fin to the amount of heat transfer inside a straight channel has been investigated numerically. It contains 1, 3 and 5 fins separately. The Carboxymethyl cellulose aqueous solution (CMC) was considered as a power–low non-Newtonian fluid. The local Nasselt numbers, heat transfer coefficient and pressure drop have been studied at some Reynolds and Prandtl number. From this study, it has been concluded that the increasing the number of fins on the wall helps to increase total heat transfer but increasing rate of heat transfer has nonlinear trend with increasing the number of fins. The rate of heat transfer has decreasing trend due to differences in flow pattern. Also, the contribution of heat transfer on the walls with and without fins is not regular process and depends on the specific location of the fins. The optimum heat transfer and pressure drop are dependent on the number and spacing of the fins. Therefore, it is necessary to balance the amount of heat transfer increased due to the increase in the number and area of the fins surface and the increase in the pressure loss associated with it.

In the present study, two analytical and numerical methods have been used for studying and testing of Functionally Graded Latticeplates in thermal environments. In the analytical method, the properties of the Functionally Graded plates are defined as a function oftemperature, and to take account of the properties of Lattice Plates, the stiffness matrix defined by V.V. Vasiliev is used. The governingequilibrium equations are obtained based on the first order shear deformation theory, which includes displacement and rotationalcomponents, and is solved by assuming the boundary conditions that are fully clamped by the energy method. By solving the problemof a special value, the vibrational behavior of the structure in a thermal environment (with the presence of thermal stress) is determined.Analytical and numerical results have been compared and verified with the results of previous works. In the field of free vibration, aFunctionally Graded Lattice plate in a thermal environment has been used to study various parameters such as changing the size of theribs, the distance between the ribs and ... for predicting structural behavior. The results show that when the temperature rises, thenormal frequency in the Functionally Graded Lattice plate decreases with the decrease of the width of the ribs and the increase in thedistance between the ribs.

Due to the various applications of planning hulls, the demand for these floats has increased. One of the important goals in designing this category of boats is achieving higher speeds One of the factors preventing this, is the longitudinal instability problem. In this regard, various methods have been proposed to prevent the occurrence of longitudinal instability in the hull, including the addition of control elements such as the interceptors, the trimtab etc. The main disadvantages of using these elements are the maintenance and control of these elements As a result, if the vessel's longitudinal instability solved in a way that does not need maintenance it will be useful and practical. In this research, a new method is proposed to solve vessel's longitudinal instability. In this method, the vessel's instability has been removed using the transverse curvature. The numerical method has been used to investigate the effect of the transverse curvature of the hull. For validation of the numerical method, a planning hull resistance test in the towing tank has been used. Cogar hull is a hardchine single-hull planning hull with constant deadrise in stern. From the empirical tests parameters such as resistance, dynamical trim and center of gravity rise are obtained, which are also used to validate the numerical method. The final results are presented in the form of curvature effect on longtitudinal instability,resistance and dynamic trim for different input velocities. According to the results, the change in the curvature has a significant effect on longitudinal instability .

Due to the side effects and drug resistance, it is impossible to impose a long term treatment. Therefore, it is desirable to provide a method for the treatment of cancer in a limited time. So, mixed chemo-immunotherapy treatment has been presented, and the mathematical model has been extended based on this new treatment protocol. The immunotherapy modifies the dynamics of the system, and the chemotherapy guides the trajectory of the system toward the preferred equilibrium point. For identifying the effective parameters on the modification of the system dynamics, the stability and the bifurcation of the system have been studied. Since the patient’s age is effective in providing treatment, a fuzzy system, based on physiological considerations, has been used to adjust the maximum dose for a young patient more than a child one and for a child patient more than an old. The simulations on three different age patients, 8, 22, and 60 years old, indicates the necessity of the provided treatment. The treatment duration in the old and child patients is shorter than the young one due to the stronger immune system assumption that shows the importance of the immunotherapy besides the chemotherapy.