flow

The paper provides an analysis of key parameters such as: heat transfer coefficients, flow, pressure drop, pump power, heat losses and temperature drop in the oil pipeline. Tests were performed on a real oil pipeline plant with a diameter of 457 mm and a length of 91000 m. The oil pipeline is dig into the ground at a depth of 1.5 m. As an experimental fluid, crude oil of the paraffinic type, with a pour point of +8 to +26 oC, was used. In order to improve transport properties and prevent the appearance of paraffin inside the pipeline, the crude oil was heated to a temperature in the range of +20 to +50 oC. Origin software was used to display the research results. An analysis of the key transport parameters and their mutual dependencies and influences is also given. The aim of the work is to analyze and determine the optimal parameters of crude oil transport, as well as to determine the relation between heating temperature, paraffin content, flow temperature and cooling rate, where oil solid content will not occur. For such research, paraffin type oil was chosen as the experimental fluid.

The self-excited oscillating cavitation jet nozzle (SEOCJN) serves as a crucial component for converting hydrostatic energy into dynamic pressure energy and ensuring optimal hydraulic and cavitation performance of cavitating jets. Thus, it is of crucial significance to understand the cavitation characteristics and the influence law of SEOCJN for its extensive industrial applications. This paper utilizes numerical simulation methods to analyze the dynamic process of cavitation initiation, development, and outlet cavitation performance of SEOCJN. It explores the effects of inlet pressure and flow rate on the frequency characteristics of SEOCJN, and establishes a mathematical relationship between self-excited oscillation frequency and outlet flow frequency. The results indicate that the self-excited oscillation nozzle has an inlet diameter (D1) of 4.7 mm, an outlet diameter (D2) of 12.2 mm, a length (L) of 52 mm, a chamber diameter (D) of 83 mm, an oscillation angle of 120°, and an inlet pressure (Pin) of 4.8 MPa. At these parameters, the frequency of the pulse jet reaches 830.01 Hz, with an internal flow period of approximately 0.0024 s. The maximum vapor volume fraction is found to be located 0.28 m from the outlet of the SEOCJN. Furthermore, the frequency of self-excited oscillation pulse increases with an increase in inlet pressure. These findings provide a theoretical basis for the industrial application of self-excited oscillation cavitation jet nozzles.

This study focuses on the flow and pressure fluctuations of a fixed displacement radial piston pump with a valve plate with silencing grooves, and the effect of the number of pistons (5, 6, and 7) is investigated. Over the manifolds of the pump, valve plate silencing grooves are regarded as Top Dead Center and Bottom Dead Center. The mathematical modeling is run in MATLAB Simulink. Analyzing the flow characteristics and volumetric efficiency of the pump with and without silencing groove valve plate configuration of the pump is done. The opening and closing area pattern of the kidney port is also analyzed. The percentage reduction of flow and pressure fluctuation with the silencing groove is 19% and 16.16%, respectively, for Z = 7, as compared to the model without silencing groove valve plate. The volumetric efficiency of the model with silencing groove valve plate is improved from 1% to 2% as compared to the model without silencing groove valve plate. The lower the flow and pressure fluctuation coefficients, the higher the flow rate and volumetric efficiency of the pump for the model with silencing groove valve plate.

A preheating exchanger is developed for improving acidic water degassing. Reasonable optimization of dualinlet swirl heating tubes is analyzed by computations of the flow and heat transfer. The comparisons of the swirl number and circumferential average Nusselt number between isobaric injection and isokinetic injection are performed. Inlet area ratios ranging from 0.1 to 0.9 exhibit an important influence on the flow phenomena and the heating performance. A lower value of inlet area ratio leads to the tendency for the fluid passing through inlet 2 to move upstream of inlet 2 and results in more vortex pairs between inlets 1 and 2. An inlet area ratio value of 0.5 exhibits the largest global average Nusselt number, normalized Nusselt number, and thermal performance factor. The optimized inlet area ratio is suitable for improving the degassing efficiency

Hydro screw is an axial micro hydro turbine of Archimedean origin. Due to ever-increasing need for clean fuel based and environmentally clean electric power, a research project was undertaken at IROST. In this study, the effect of spiral variable pitch on hydro screw turbine has been studied numerically. Based on the results, it was found that the turbine had the best efficiency with a spiral pitch of 1.5. Accordingly, the small model of this turbine was made and tested in the laboratory. The results indicate that the numerical results of the calculations are in good agreement with experimental result, and therefore they can be used safely in the course of subsequent turbine studies. In summary, the results indicate that the maximum turbine output is between 62% and 68% which is about 30% higher than the constant pitch blade turbine.

Currently, there are different computational fluid dynamic (CFD) techniques used to obtain the flow around trains. One of these techniques is the Reynolds-averaged Navier-Stokes (RANS), which is commonly and widely used by industry to obtain the mean flow field around trains in different operating conditions. In order to assess the performance of RANS turbulence modelling for train aerodynamics, five different common RANS modelling have been used in this paper to obtain the flow and the surface pressure around a simplified train model subjected to crosswind; the standard k- model, the realisable k- model, the Re-Normalisation Group (RNG) k- model, the standard k- model and Shear Stress Transport (SST) k- model. The train model was stationary and subjected to crosswind with a 90o yaw angle. The effects of mesh size and spatial discretization scheme on the aerodynamic characteristics of the train were also investigated. The results obtained from the different RANS models were compared to those from published experimental data. In general, all the RANS models provided the pressure distribution trend. However, all k- models overestimate the surface pressure on the train body except the bottom face. The standard k- model underestimates the surface pressure on the train body except the streamwise face. It was shown that the simulation using SST k- model together with a second order discretization scheme provides the closest results to the experimental surface pressure. It could be concluded from the present study that the SST k-model with a second order discretization scheme and y+ around 1.0 is the most appropriate RANS model for simulating the flow around trains subjected to crosswinds.

A series of bench scale experiments were performed to assess the effects of biofilm and bio-enhanced toluene dissolution on flow and solute transport through a rough fracture. The fracture was cast from a real shale rock fracture. Sterilized artificial groundwater was used as the nutrition source to support the growth of microorganisms which were obtained from local groundwater. Hydraulic and tracer tests were carried out before and after the injection of toluene, and during the toluene biodegradation as well. The normalized hydraulic conductivity decreased sigmoidally during the experiment, and reached 0.02 at the end of the experiment. Biofilm growth was the main cause for hydraulic conductivity reduction after the injection of liquid toluene. The presence of separate phase toluene extended the tracer tailing compared to tracer tests without toluene. The longitudinal dispersion coefficient DL was proportional to the 1.5th power of the mean velocity in the rough fracture with or without residual toluene. Though a biofilm developed in the fracture during biotreatment, the effect of secondary biofilm-associated porosity on solute transport in the fracture had negligible effect on tracer transport due to its small thickness. It is also found that DL decrease exponentially with Pe reduction during the bio-treatment.

This paper presents a theoretical study on wood plastic composite's (WPCs) flow, based on empirical data provided by a twin screw extruder and experimental data from a rotational rheometer. Four circular extrusion dies were designed and manufactured to produce rod shaped products with various diameters (D) and length-to-diameter ratios (L/D). Also other parameters such as screw speed (N), polymer matrix type, polymer viscosity (m) and percentage of wood content (W) were selected as the process or material factors to investigate the relationship between the flow characteristics and the above mentioned factors. Moreover, frequency sweep experiments were performed on the selected composites using rotational plate rheometer. The results from these experiments have been studied by using power law and Bingham plastic models which are believed as proper models for WPC in the literature. The results show that Bingham plastic model can explain the flow characteristics of this composite much better. Moreover, although the results of a frequency sweep test can give the required values for parameters in the Bingham plastic model, these quantities will be different with those from empirical experiments.

To estimate the maneuverability of a submarine at the early design stage, an accurate evaluation of the hydrodynamic coefficients is important. In a collaborative exercise, the authors performed calculations on the bare hull DRAPA SUBOFF submarine to investigate the capability of viscous-flow solvers to predict the forces and moments as well as flow field around the body. A typical simulation program was performed for both the steady drift tests and rotating arm tests. The same grid topology based on multi-block mesh strategy was used to discretize the computational domain. A procedure designated drift sweep was implemented to automatically increment the drift angle during the simulation of steady drift tests. The rotating coordinate system was adopted to perform the simulation of rotating arm tests. The Coriolis force and centrifugal force due to the computation in a rotating frame of reference were treated explicitly and added to momentum equations as source terms. Lastly, the computed forces and moment as a function of angles of drift in both conditions are compared with experimental results and literature values. They always show the correct trend. Flow field quantities including pressure coefficients and vorticity and axial velocity contours are also visualized to vividly describe the evolution of flow motions along the hull.

The purpose of this paper is to studying nonlinear k-ε turbulence models and its advantages in internal combustion engines, since the standard k-ε model is incapable of representing the anisotropy of turbulence intensities and fails to express the Reynolds stresses adequately in rotating flows. Therefore, this model is not only incapable of expressing the anisotropy of turbulence in an engine cylinder, but also is unable to provide good performance when computing the swirling and tumbling flows is important in engine cylinders. Thus, in this paper, the results of nonlinear k-ε model are compared with those of the linear one. Results of diesel engine simulation with linear and nonlinear k-ε models in comparison show that turbulence intensity in the nonlinear model simulation is higher than that of the linear model; also, nonlinear k-ε models predict the second peak value because of the bowl shape in expansion stroke for turbulence intensity. Gas injection results show that nonlinear turbulence models predict spray penetration accurately because of correctly turbulence intensities predicting. Also, the results demonstrate that, for high pressure gas injection, turbulence intensity is high and predicted accurately using nonlinear models. Then, its spray penetration length is predicted accurately in comparison to experimental data’s. Although CPU time spending in the nonlinear model is more than that of the linear one, the non-linear stress model is found to increase computation time by 19%.