TURBULENCE MODELS have long been developed and examined for their accuracy and stability in variety of environments. While many flows work with excited TURBULENCE intensity, MODELS have rarely been tested to explore whether their accuracy withstands with augmented free stream TURBULENCE intensity or decline in reasonable solutions. In present study the turbulent intensity of the air, moving parallel to a flat plate is increased from 0.4 to 6.6% for the whole flow, downstream to the screen. Three popular TURBULENCE MODELS are examined by investigating the TURBULENCE penetration into flow field as well as into turbulent boundary layers over the flat plate. Results of numerical solutions for Standard k-e, Realizable k-e and finally two equations Shear Stress Transport k-w model are compared to experimental measurements and results are discussed. Results of variation of free stream TURBULENCE intensity from flow field out of boundary layer, in addition, streamwise mean velocity, streamwise rms velocity and skin friction coefficient from boundary layer are investigated. Conclusion is made that despite restrictions of these turbulent MODELS specially in predicting flow near a turbulent/non-turbulent interface, they have acceptable performance in both low and high intensity turbulent flows.

There are many approaches to determine the sound propagated from turbulent flows. In hybrid methods, the turbulent noise source field is computed or modeled separately from the far-field calculations. To have an initial and quick estimation of the sound propagation, less computationally intensive methods can be developed using stochastic MODELS of the turbulent fluctuations. In this paper, turbulent mean flow of a two dimensional, compressible, cold-jet at Mach 0.56 is computed using RANS with 2 equation k-e RNG model. The above mean-flow quantities are then used in a stochastic model to generate the details of the turbulent velocity fluctuations. This method is based on the use of classical Langevin equation to model the details of fluctuating flow field superimposed on the averaged computed quantities. The resulting sound field due to the generated unsteady flow is then evaluated using Lighthill's acoustic analogy. Our results are validated by comparing the directivity and the overall sound pressure level (OASPL) magnitudes with the available experimental data. Numerical results show reasonable agreement with the experiments, both in maximum directivity and the magnitude of the OASPL.

In this paper, linear accelerated turbulent pipe flow has been simulated at various Reynolds numbers using five common TURBULENCE MODELS. The MODELS considered are the Baldwin-Lomax algebraic model, the Spalart-Allmaras one-equation model, theκ-e model with wall correction of Lam and Bremhorst, theκ-ω model and the κ-ε-ν2 model. The goal is to evaluate the performance and precision of these MODELS for prediction of the wall shear stress, Reynolds stress, TURBULENCE viscosity, delay time in response and mean velocity. Factors such as changes in pipe diameter, fluid type, initial Reynolds number of acceleration and rate of acceleration and its effect on the above parameters has examined carefully. In order to verify the results, the experimental and numerical results (TURBULENCE modeling and Large Eddy Simulation) of other researchers have been compared with the present results. The results show the desired accuracy of the one-dimensional modeling of accelerated turbulent pipe flow in comparison with Large Eddy Simulation results (three-dimensional). The response of delay time, simulated by the MODELS (except BL model) shows relatively good agreement with experimental data. Comparing the distribution of mean velocity, turbulent kinetic energy and turbulent viscosity shows  k-e-ν2 model leads to a better accuracy compared with the other MODELS.

Distillation Column is one of the eldest and important separation equipments which many new designs and various changes in its internals are still being made for increasing its performance. In this research with utilizing computational fluid dynamics, sieve tray hydraulics in experimental scale has been simulated in two phase and three dimensions in Eulerian frameworks by FLUENT 6.3 commercial software. And the simulation have been validated with Krishna et al. (1999) experimental and simulations results. Then simulating with RSM and k-e in three forms of Standard, Realizable and RNG TURBULENCE MODELS, the results have been discussed and compared and has been demonstrated that the RNG model predicts lower clear liquid height which are closer to the experimental results.

In the current study, after validating the accuracy of the current solution, mixed convection heat transfer in a square enclosure for drilling mudas a non-Newtonian fluidand wateras a Newtonian fluid—is investigated by finite volume method. The TURBULENCE methods used in this study are the reliable methods such as RNG, standard, and RSM. The outcome of the investigation implies that under natural convection conditions, velocity boundary layer is somewhat asymmetrical on the cold wall and the fluid at the center of enclosure remains stratified and still. The existing graphs also indicate that the TURBULENCE intensity is higher for forced convection than natural convection. Also, the maximum TURBULENCE intensity is greater for drilling mud than water. One of the most prominent outcomes to be named is that, under similar circumstances, the Nusselt number for water is far more than the one for drilling mud, which confirms that convection heat transfer is greater in the water than the drilling mud.

In this study, modeling of a fuel jet which has been injected by high pressure into a low-pressure tank are investigated. Due to the initial conditions and the geometry of this case and similar cases (like CNG injectors in internal combustion engines (ICE)), the barrel shocks and Mach disk are observed. Hence a TURBULENCE and transient flow will be expected with lots of shocks and waves. According to the increasing usage of this type of injectors in ICE, more studies should be conducted to find the most accurate and beneficial MODELS for modeling this phenomenon. In order to find an accurate and beneficial TURBULENCE model, in this study, three Reynolds-averaged Navier– Stokes (RANS) TURBULENCE MODELS (SST k-ω , RNG and standard k ) and large eddy simulation (LES) TURBULENCE model were compared by the fuel jet characteristics in three regions (outlet of the nozzle, at Mach disk and at the downstream of the flow). Although the LES model needs more time for each test, the results are more reliable and accurate. On the other hand, RANS TURBULENCE MODELS have lots of errors (more than 10 percent) especially for predicting the characteristics of fuel jet at Mach disk.

TURBULENCE schemes have long been developed and examined for their accuracy and stability in a variety of environments. While many industrial flows are highly turbulent, MODELS have rarely been tested to explore whether their accuracy withstands such augmented free-stream TURBULENCE intensity or declines to an erroneous solution. In the present study, the TURBULENCE intensity of an air flow stream, moving parallel to a flat plate is augmented by the means of locating a grid screen at a point at which Rex=2.5×105 and the effect on the flow and the near-wall boundary is studied. At this cross section, the TURBULENCE intensity is augmented from 0.4% to 6.6% to flow downstream. Wind tunnel measurements provide reference bases to validate the numerical results for velocity fluctuations in the main stream and at the near-wall. Numerically, four of the most popular TURBULENCE MODELS are examined, namely the one-equation Spalart-Almaras, the two equation Standard k-e, the two equation Shear Stress Transport k-w and the anisotropy multi equation Reynolds Stress MODELS (RSM). The resulting solutions for the domain are compared to experimental measurements and then the results are discussed. The conclusion is made that, despite the accuracy that these TURBULENCE MODELS are believed to have, even for some difficult flow field, they fail to handle high intensity TURBULENCE flows. TURBULENCE MODELS provide a better approach in experiments when the TURBULENCE intensity is at about 2% and/or when the Reynolds number is high.

Turbulent wind flow over buildings occurs due to the complexity like sharp corners, ground effect and different vortexes is one of the best choices to evaluate TURBULENCE methods. DES and DDES are hybrid RANS-LES MODELS for simulating turbulent flow which for their characteristic treat near wall as RANS and farther the wall act as LES model. Consequently computational time will decrease compared to traditional LES MODELS. In this article to evaluate DES and DDES MODELS, turbulent incompressible flow in Re=22000 over 3D building is simulated using parallel processing facilities. For verification purpose other investigators experiment results are used. Also the mentioned MODELS are compared with classic RANS and LES MODELS, like k-e and LES-Smagorinsky to depict their performance. Our results illustrate DES model with fine grid has good precision for simulating turbulent incompressible wind flow over building and decline of 26 percentage of computational time compared to LES-Smagorinsky model.

In this paper, transient flow in a pipe at Reynolds numbers (based on bulk velocity and diameter) ranged from 7000 to 45200 is numerically simulated using four common TURBULENCE MODELS. The MODELS considered are the Baldwin- Lomax algebraic model, the k-w model with wall correction of Lam and Bremhorst, the e-w model and the k- e-v2 model of Durbin. The results of these MODELS are compared with those of the recent experiments reported in the literature. The predicted velocity and delay period using the MODELS compared well with measured values for short and long ramp-up flow excursions. The delay period of the calculated TURBULENCE kinetic energy close to the pipe centerline is around 4 sec which agrees with the experiments. The k-e-v2 model was found to provide the best results compared to the measured data in the region away from the wall. At the end of the excursion near the wall, however, the results of this model differs from those of the experiments.