numerical simulation

Plasma technology is used in many countries in various fields such as ozone production, surface treatment, surface modification, medicine, etc. Plasma generated with microwave-like waves is a promising and interesting technology for its unique and versatile properties. These characteristics of microwave plasma make it an alternative technology compared to traditional thermal chemical reactors, provided that its specific technical challenges are met. In this numerical study, the properties of microwave plasma with a frequency of 2.45 GHz and argon gas at atmospheric pressure were investigated. By varying the input power of the device in the range of 10 W to 20 W in magnetic mode and mode (TM), the comparative profiles of electron density, electron temperature, electric field are shown. The simulation results show the production of chemical elements in microwave plasma. High-energy electrons and electron density are considered as the main factors affecting the properties of microwave plasma.

This research explores the fundamental mechanisms underlying electrical discharges in dielectric barrier discharge (DBD) reactors. Specifically, we investigate how voltage parameters, such as amplitude, frequency, and waveform, affect plasma characteristics .Numerical simulations reveal that alterations in these parameters can significantly impact the spatial distribution of energy within the plasma. These findings demonstrate that precise control over plasma properties can be achieved through fine-tuning voltage parameters, thereby optimizing DBD reactor performance for applications such as treating water contaminated with volatile organic compounds, generating high-purity ozone for medical purposes, and depositing thin polymer films. This research represents a significant step forward in the design and operation of DBD reactors across various industries.

In this research, different tandem solar cells have been designed and simulated, in which the upper sub-cell is Sb2S3. Different structures including Sb2Se3, CISe, CZTSe and GeTe were proposed for the lower sub-cell.It is very important to match the current in the upper and lower sub-cells in consecutive cells. To reach the current matching point, the thickness of the layers of the lower sub-cell was kept constant and the thickness of the absorbing layer of the upper cell was changed so that the current density in both sub-cells was the same. At the current matching point, the performance of the upper cell under the AM1.5G standard spectrum radiation and the performance of the lower sub-cell under the filtered spectrum radiation were evaluated, and then the current-voltage characteristic curve of the tandem cell was obtained from the sum of the characteristic curves of the two sub-cells. The efficiency obtained for Sb2S3/Sb2Se3, Sb2S3/CIS, Sb2S3/CZTSe and Sb2S3/GeTe tandem cells was 22.10%, 30.95%, 24.83% and 36.80%, respectively. The greater the energy gap difference of the sub-cells, the more photons are collected and the greater current density is obtained for the cell. The best performance was obtained when GeTe was used as the bottom sub-cell.

In the last two decades, photonic crystals and structures that are based on them (photonic structures) have been examined and have been widely utilized in various optical applications. In this article, a theoretical and numerical model for the propagation of electromagnetic waves in multilayer dielectric structures is developed. The propagation of ultra-short light pulses in multilayer media and microresonators is investigated, and the energy reflection and transmission coefficients depending on the parameters of the environment and duration of the optical pulse are calculated. A method for calculating the transmission and reflection spectra of one-dimensional photonic crystal based on FDTD modeling with the emission of ultra-short optical pulses is proposed. To calculate the transmission and reflection spectrum of a one-dimensional photonic crystal and to simulate the propagation of ultra-short light pulses, in multilayer dielectric structures and microresonators, based on the numerical solution of Maxwell's equations with the finite difference approximation in the space-time domain, is performed.

In the process of crystal growth by Czochralski technique, lower part and core of the crystal are warmer than other parts of crystal and its environment, which leads to expansion in different parts of the crystal. The result of this thermal gradient is strain, which eventually causes thermo-elastic stress in the crystal. Increasing this stress leads to transition of the material from elastic limit and entering plastic area. To show thermo-elastic stress in crystals, a criterion called Von Misses stress is used. Using the solid mechanics approach, the mechanical response of crystal to the stresses can be determined through appropriate structural equations. In this paper, using appropriate structural equations, a set of numerical simulations of temperature field, thermal stress and dislocation density for a Czochralski setup used to grow Ge single crystal have been done for different heights of crystal. In order to investigate dislocation density, using a simple first-order approximation, in which the dislocation density is proportional to radial gradient of temperature is used. A two-dimensional steady state finite element method has been applied for all calculations. The numerical results reveal that the thermal field and thermal stress are mainly dependent on the crystal height, heat radiation and gas flow in the growth system. As the height of the crystal increases and the shape of the crystal-melt interface changes, we see an increase in thermo-elastic stress and dislocation density.

Researchers have recently paid a lot of attention to drag force estimation over different bodies. This force is usually calculated using surface integral over the body and momentum defect method in the wake region. In this research, the steady-state, incompressible drag force calculation around a submarine model is numerically investigated using the latter technique (momentum defect method). Simulations were carried out at different aspect ratios at zero angle of attack and the capabilities of this method at inclined flows were also investigated. The most important parameters which affect the results are the vertex space, the distance of data collection section, and the data collection section size. In this article, practical suggestions are made for each parameter. The contribution of the pressure, momentum, and turbulence term were also evaluated at different cross sections. These findings can be implemented in wind tunnels with small test section length. They can also be used to compare the results with the common CFD surface integral method. By using the results of this research, the maximum error implementing this technique at zero and non-zero angle of attack will be about 4% and 16% respectively.

The performance of a uranium gas centrifuge which is used in the uranium enrichment industry depends strongly on the gas flow field. The computer simulation is vital to examine the gas flow field. Therefore, in the present study, the capabilities of OpenFoam software for simulating the gas flow inside the rotor for total reflux thermal drive-in axisymmetric mode has been investigated. The results corresponding to the OpenFoam ssimulation have been validated with those of analytical Olander’s model, numerical solution of the Harada’s study, and simulation using Fluent. The simulation results for gas flow inside the rotor of centrifuge showed that the density-based solver was properly chosen and the number of cells, 160×170, was compatible with mesh. The numerical results show that OpenFoam software was capable to examine the gas flow inside the rotor. Also, the simulation of the distribution of Knudsen number confirms the presence of the molecular region near the axis of rotation. OpenFoam is open-source software and there is the ability to solve the molecular region as well as the coding for coupling the continuous and molecular region, the feature which does not exist in the fluent software. The use of open foam is therefore recommended to simulate gas flow inside the rotor.

Since the wind pattern on various activities in islands as well as its effect on other meteorological parameters is important long – term temporal and spatial variations of the wind field are studied. Here, the warmest month (July) and the coldest month (January) 2015, are selected in order to test the sensitivity of low-level wind simulations of the Weather Research and Forecasting (WRF) model to the parameterizations of the boundary layer (PBL), the surface layer (SL) and the land surface (LSM) over Qeshm Island. As this work was focused on the simulation of near-surface and vertical wind profiles, the physical options related to the parameterizations of boundary layer processes (SL, PBL and LSM) that have significance influence for this purpose are validated. Although more physical options are available in the model (for cumulus convection, short and long wave radiation, microphysics and etc.), it is not feasible or necessary to include all the model configuration options in the sensitivity analysis to obtain an efficient model configuration optimization. The model grid comprised of four nested domains at horizontal resolutions of 45, 15, 5 and 1 km respectively. The innermost domain (D4) with 1 km spatial resolution covered the chosen area to simulate PBL wind field over Qeshm island region. The results of the simulations under five different configurations are validated with the observational wind speed data of Qeshm Airport and Marine Qeshm Stations. The results demonstrate that in both episodes, the ACM2 boundary layer scheme has presented the best performance in combination with the Pleim - Xio surface layer and the Noah land surface schemes because it considers vertical mixing both local and non-local in simulation of planetary boundary layer wind structure. The simulations of WRF are sensitive to warm and cold seasons as well as selected parameterizations. After selecting the appropriate configuration, the simulation of the wind field for one year was carried out to investigate the low level wind field, the vertical structure of the boundary layer wind and the impact of the land mask distribution on and around the Qeshm Island. These simulations indicate higher wind speed in spring and summer and the roughness of the island causes a low level wind convergence, then turn to the left on the Strait of Hormuz with decreasing wind speed. Monthly average of the wind direction during the daytime of reference month of each season are generally simulated to be southwesterly (January, April, July, October) and during the nights of January and July it is southerly to southeast and in April and October it is simulated southwesterly. The direction of the wind has significant variations at sunrise and sunset due to changes in regional scale forcing and baroclinicity behavior between the sea and the coast. Surface roughness in coastal areas, strait narrowing and sea breeze, enhance the low-level jet during summer and spring middays at altitudes of about 180 to 200 meters. In other words, we can say these low-level jet (Shamal winds) during summer and spring occurs as a result of the interaction of two pressure systems; the heat low pressure cell (low level cyclone) over Iran and a semi-permanent high over northwestern Saudi Arabia and it acquires some convergence because of the these factors.

The widespread use of squirrel cage fans, especially in ventilation and home and industrial environments, has led to the formation of many research efforts to improve performance and reduce the sound produced by this type of fan. In the literature, the most important factor in generating sound in this category of fans is the confrontation between the rotor exit flow and the volute of the fan. In this research, a numerical study was conducted to solve the unsteady fluid flow inside the fan, calculate the pressure fluctuations on the fan body and the intensity of this pressure field in different areas of the body, the study of the contribution of different areas of the body to the sound field fan and, and estimate the sound field pattern of fan. The results show a fluctuating pressure on the volute that is due to the collision of the jet-wake rotor exit flow with the volute. Also, the maximum contribution of the cut-off adjacent regions was observed in the formation of a dipole sound radiation pattern. Another main observation was the insignificant rotor's contribution in sound filed compared to the volute.

The tide is an essential information in conducting studies on sedimentation, morphological changes and flooding of coasts, erosion as well as coastal strip management. Due to lack of measurement information in many coastal and marine areas, wave characteristics are estimated using different methods. Marine wave forecasting projects are often performed by numerical models or empirical methods. In the present study, the tidal flow velocity in Bushehr Bay is modeled using the numerical model TELEMAC-2D and the dominant flow direction in the area is analyzed. Model settings include irregular trigonometric grid in x and y with the ratio of one to three from the smallest 30m grid to the largest 810m grid, a time step of 30 seconds, the bed friction law using Stickler Theory 50 m1/2s-1  used. The model ran for one month on 2011/07/12 in the Bushehr Bay. After running the model, the current velocity data are compared with the corresponding measurement data and the TPXO Global Database, the results showed an increase of correlation from 41/86% to 91/41% indicating that the model is suitable for flow rate modeling in Bushehr Bay. At the end, the dominant flow in the northwest is presented.

Tsunami is an oceanic gravity wave generated by the displacement of huge volumes of water. There are three main types of disturbances: underwater earthquakes, submarine landslides and sudden earth surface movements adjacent to the ocean (volcanoes, meteorites, rock falls, sub-aerial landslides and ship sinking). Most tsunamis are caused by large shallow earthquakes in subduction zones (Satake and Tanioka, 1999). Sumatra–Andaman (2004) and Honshu, Japan (2011) tsunami events and following widespread damages and tragic consequences demonstrated the need of worldwide attention, awareness and preparedness for tsunami hazard mitigation. While the world draws its attention to tsunamis in the Indian Ocean, further attention is increased in the eastern areas of the Indian Ocean near Indonesia. Western Makran is located in the northwestern Indian Ocean basin. It has received less attention as a potential tsunamigenic zone. The Makran region is a 1000-km section of the Eurasian-Arabian plate boundary and located offshore Pakistan in the northwestern Indian Ocean where the oceanic crust of Arabian plate is being subducted beneath Eurasian plate since the Early Cretaceous along a north dipping subduction zone (Byrne et al., 1992; Smith et al., 2013). Following the great earthquake in Pasni-Ormara on 1945.11.27, Mw=8.1 (Byrne et aL, 1992), the coastline uplifted by about 2 m (Page et al., 1979). This event was accompanied by a significant regional tsunami, with run-up in the 5–10 m range which caused about 4000 deaths along the very sparsely populated Makran coast (Heck, 1947; Ambraseys and Melville, 1982; Okal and Synolakis, 2008). The Makran may be seismically segmented along its length into a western and an eastern segment, distinguished by different levels of seismicity (lower in the west). Moderate to large magnitude earthquakes are either related to the down going slab at intermediate depths or superficial in the eastern Makran (e.g. 1765, 1851 and 1945 earthquakes), while western Makran is marked with almost no seismicity in the coastal area at present but might have experienced a strong earthquake in 1483 (Byrne et al., 1992; Zarifi, 2006).
The lack of earthquakes for many years has increased the possibility of locking the western Makran segment. This means that, it could generate a potential tsunami event in the future that can threat the Gulf of Oman and the Makran coastlines. Because of the tsunamigenic potential of Makran subduction zone, also importance of strategic geographic location, financial role of Makran coast in Iran, accessibility to international waters, ability to communicate with other countries and its cultural, natural and historical tourism potential along with the establishment of ports and coastal and offshore installations in the region, tsunami can be a real threat. Consequently, it is indispensable to have accurate studies and estimates for tsunami risk mitigation. The aim of this study is to simulate tsunami generation in western Makran numerically for estimating the initial condition for tsunami propagation. Tsunami generation mechanism should be modeled as the first step in the process of tsunami modeling. The generation modeling problem should be studied geophysically and geologically, therefore it is a very important and vital stage in tsunami simulation. To estimate the static uplift of seafloor, we can use the fault models e.g., Okada (1985) and Mansinha and Smylie (1971) which are the analytical solution of deformation field caused by instantaneous rupture on an elastic finite fault plane. The theory was proposed originally by Mansinha and Smylie (1971) and then improved by Okada (1985). We need the fault parameters (Hypocenter (Latitude, Longitude and Depth), Length and Width of Fault Plane, Dislocation (Slip), Strike direction, Dip angle and Rake (slip) angle) to compute the deformation. A tsunami scenario with defined source parameters was constructed in the Gulf of Oman to compute the deformation field based on the Okada algorithm. The source model was based on Okal and Synolakis (2008) and Smith et al. (2013) with a length of 450 km, a width of 100 km and a dislocation of 10 m which has a moment magnitude (Mw) of 8.7. The result of this study represents the initial profile of the tsunami while including the uplift and subsidence in the study area. The earthquake scenario predicted maximum seafloor uplift of 3.5 m and maximum subsidence of 2.4 m. The deformation field covered an area from 23.5° N to 27.5° N and from 56° E to 63° E. The southern coastal areas of Iran and Pakistan experienced subsidence and the northern coastlines of Oman experienced uplift. The outcome can be used as the input in the simulation of tsunami propagation

Tsunami numerical modeling is a mathematical description of tsunami life cycle circle including generation, propagation and run-up. Numerical simulation is a powerful tool to understand the impacts of past and future events. It is critical to use the results of tsunami simulation such as tsunami waves propagation patterns, time series, amplitudes and run-up along coastlines to mitigate tsunami hazard of possible future events. Tsunami waves propagate with a velocity up to 700 to 950 km/h in the ocean without losing a lot of energy. As they reach shallow waters, their amplitude grows larger in the wave shoaling process. Nonlinear shallow water equations are often used to model tsunami wave propagation and run-up.
The aim of this study is simulation of tsunami wave propagation and run-up in the western Makran for a tsunamigenic scenario capable of generating a Mw 8.7 magnitude. The initial condition to of model the tsunami propagation is computed using the Okada's algorithm. The COMCOT hydrodynamic model is used for the numerical tsunami simulation. The COMCOT is capable of solving non-linear shallow water equations in both Spherical and Cartesian coordinates using explicit staggered leap-frog finite difference schemes and a nested grid configuration.
Tsunami propagation is highly influenced by the bathymetry. A three level nested grid system with different resolutions is used for tsunami simulation in this study. Configuring a nested grid system in tsunami modeling is necessary to compute tsunami run-up and inundation on dry land. The simulation is then performed for a total run time of 90 minutes with a time step of 0.5 min for the parent grid and 0.0625 min for the finest grid. Numerical modeling of tsunami run-up and inundation is performed for the western (C1), central (C2) and eastern (C3) parts of the Makran coastline in the south of Iran.
The trapping of tsunami waves inside the Gulf of Oman causes more impacts on the coastlines of Iran and Oman in comparison to the other areas. To investigate the time histories of tsunami waves after the generation by the tsunmigenic scenario, we put 18 virtual gauges near and along the southeastern coastline of Iran. Generally, it takes about 20 minutes for maximum tsunami wave amplitudes to be observed at the southeastern coastlines of Iran. The maximum tsunami wave heights computed for the gauges near Jask and Chabahar are 2/8 and 3/3 m respectively. The entire southeastern coastline of Iran is impacted by such tsunami waves. The maximum computed tsunami wave height along the southeastern coastline of Iran is 11m.
The maximum tsunami wave field exhibits a significant local hazard field inside the Gulf of Oman posed to the shores of Iran and Oman. The maximum tsunami amplitude reaches up to 11 m and 6 m inside the Gulf of Oman the Arabian Sea Basins, respectively. The results of run-up modeling show that the maximum computed run-up for the C1, C2 and C3 areas are 10, 17 and 19 m. The maximum tsunami inundation distance for those areas are 6, 6 and 4 km, respectively. The considerable values of inundation distance are due to low elevation topography of the affected coasts. Computing the tsunami inundation distance can be used in choosing evacuation lines during the possible future tsunamis and finding safer locations along the coastal areas. Accurate tsunami simulations are required to develop a tsunami early warning system and estimate the tsunami inundation on dry land. To perform more accurate simulations, high resolution local bathymetric/topographic maps are required, especially for the major ports in southeastern Iran

A fluid، which is stable under the action of buoyancy، can oscillate under the influence of buoyancy and Coriolis forces. The resulting ageostrophic oscillations with a frequency between Coriolis and buoyancy frequencies are called inertia-gravity waves، hereafter IGWs. In this study we investigate the generation and propagation of IGWs over Iran. To this end، the Weather Research and Forecasting (WRF) mesoscale model is used to simulate an event with noticeable IGWs within a synoptic system accompanied by rain and snow، from 6 to 9 February، 2012. The NCEP FNL data (final analyses) are used for this simulation in a domain of 8000 km × 6375 km extent and a medium resolution (grid interval Δs=25 km). The model has 35 levels in vertical direction with its top at 10 hPa (~30 km). A time step of 150 seconds is used and the model is run for 72 hours initialized at 12UTC 6 February and continued until 12UTC 9 February 2012. An implicit Rayleigh damping layer is used to prevent unphysical wave reflection from the upper boundary of the computational domain (Klemp et al، 2008). In order to investigate generation and propagation of IGWs and to determine the effects of each of energy sources in the region، four different model runs are designed and performed with/without orography/moisture. In order to facilitate the conduct of the study، the main area of interest is classified into three regions where the IGWs are most active. The first area is located in the northwest of the country، in the vicinity of the maximum wind speed of the midlatitude jet stream and the left side of the jet streak. The second area، including the central and southern Zagros Mountain، is located in the vicinity of unbalanced flow and the right side of the jet streak. The third area is located geographically at the conjunction of Zagros and Alborz mountain ranges، is at the exit region of the jet stream and along a rain belt with significant cloud coverage as in the second area. The fundamental quantities of wave like the wave frequency and periods، the intrinsic phase speed، the group velocity and horizontal and vertical wavelengths are obtained based on the horizontal divergence field as the main quantity. This is possible، because the procedure avoids explicit treatment of the background field، which has zero divergence، and is applicable to waves of arbitrary wavelength. Previous studies have shown that the most important energy sources for IGWs are: jet streams، fronts، convection and orography. Furthermore، the IGWs propagate in the atmosphere with a phase speed of 15 to 35 ms-1، vertical wavelength of 500 m to 15 km and horizontal wavelength of 50 to 1000 km. In the reference run (with the topography and moisture included)، the distribution of the horizontal divergence clearly shows the waves closely follow the major topography and propagate nearly perpendicular to it. Estimation of wave properties shows that a high- frequency wave with is emitted in this case. The quantity is the estimate for wave frequency scaled by inertial frequency. In the first and second areas، the typical values of the horizontal wavelengths are from 150 to 175 km، the vertical wavelength from 5 to 6 km and intrinsic phase speed from 15 to 19 ms-1. In the third area، the IGWs travel with a phase speed of about 15 to 21 ms-1 and horizontal and vertical wavelengths of 100 to 120 km and 5 to 6 km، respectively. Based on the characteristics of the IGWs and their propagation، it can be inferred that the waves are generated in the troposphere by jet-front mechanisms due to topography and then undergo deformation. Some of the waves generated in the upper troposphere cross the tropopause and propagate well into the stratosphere. Disregard of the way wave are generated، this transfer of activity from troposphere to the stratosphere is a common phenomena. The results of this study are in good agreement with those obtained by Zhang and Koch in 2000 who studied simulation over Rockies Mountain in Montana and Dakota. They estimated a single wave packet with 3 or 4 waves، a wavelength of 150 km and phase speed of 15. 2 ms-1. Zulick and Peters in 2006 identified two wave packets in their study. The first wave packet included large waves with wavelengths of about 500 km and period of approximately 10 hour which were classified as sub-synoptic (or meso-α). The second wave packet، however، consisted of small waves with much higher frequency than the first wave packet، and wavelengths of almost 200 km and period of nearly 5 hour، which were classified as meso-β (mesoscale-β). Having investigated the possible energy sources in the region، the following conclusions can be made. In the run without either orography or moisture، large-amplitude waves are observed that carry energy upward to the stratosphere and downward to the troposphere. Entering a positive feedback، the downward propagating waves emitted by the jet can facilitate convective activity at lower levels and play a role in enhancing precipitation. Although adding mountains to the physics of the model affects wave characteristics like intensity، amplitude، and direction of propagation، the presence of all of the factors is necessary for describing the actual wave generation and propagation processes.