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turbulent-flow
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Experiments on pulsation effects in turbulent flows, Part I: Investigation on Simple Shear Flows
, Article Scientia Iranica ; Volume 10, Issue 2 , 2003 , Pages 238-247 ; 10263098 (ISSN) ; Hajilouy, A ; Farshchi, M ; Souhar, M ; Sharif University of Technology
Sharif University of Technology
2003
Abstract
This article describes the results of experimental observations in pulsating Simple Shear Flows (SSF). A uniform-mean-gradient shear flow was generated within the test section of an open circuit wind tunnel. Transverse arrays of honeycomb channels with differing resistances were used to generate shear flow at low shear rates (less than 20 s-1). A set of rotating vanes pulsated the flow field at 8.5 Hz and 18 Hz. Instantaneous velocity was measured by employing a two-component hot wire anemometry technique. The experimental credibility of the facility was established in stationary SSF. In pulsating flows the pulsation effects on mean shear rate, the kinetic energy of turbulence, Reynolds...
Experiments on pulsation effects in turbulent flows, Part II: Investigation on grid-generated turbulence
, Article Scientia Iranica ; Volume 10, Issue 2 , 2003 , Pages 248-251 ; 10263098 (ISSN) ; Hajilouy, A ; Farshchi, M ; Souhar, M ; Sharif University of Technology
Sharif University of Technology
2003
Abstract
In this paper, pulsating grid-generated turbulence is studied. A two-component hot wire anemometry technique is used. The pulsation effects on characterizing lenght scales and the statistical description of fluctuations are studied in comparison with their stationary counterparts. No significant change in the character of the turbulent flow with pulsation is observed
Oil-soluble drag-reducing polymers [electronic resource]
, Article Journal of polymer materials ; December 1994, Volume 11, Number 4; Page(s) 239 To 247 ; Pourjavadi, A ; Nadali, M ; Sharif University of Technology
Abstract
This article reviews the oil-soluble polymeric drag-reducing agents (DRAs) with an outlook to their large-scale application in petroleum industry. A general discussion on mechanism of the DR phenomenon and mechanical degradation of the drag reducers in turbulent flow is offered with an emphasis on the molecular parameters. Furthermore, low charge density associating polymers, as a new class of oil-soluble flow improvers, are described
Computational Simulation of Flow over a Cylinder in Ground Effect, Using PANS
, Article Life Science Journal ; Volume 10, Issue SUPPL 8 , 2013 , Pages 195-202 ; 10978135 (ISSN) ; Salimi, M ; Taeibi Rahni, M ; Mahdavimanesh, M ; Sharif University of Technology
2013
Abstract
Recently, very large eddy simulation approach has attracted a great deal of attention among researchers. This approach can be thought of as an intermediate approach in flow field filtering view point compared with Direct Numerical Simulation and Reynolds-Averaged Navier-Stokes. One famous method to this approach is Partially Averaged Navier-Stokes. Early studies have demonstrated the capability of this technique in flow prediction; however, this method still needs to be evaluated under more flow conditions to ensure its reliable performance. In this study, the performance of PANS k-ω method in the simulation of turbulent flow around a cylinder with square cross section close to a flat...
Experimental investigation of turbulence specifications of 3-D density currents
, Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 1 SYMPOSIA, Issue PART A , August , 2007 , Pages 789-796 ; 0791842886 (ISBN); 9780791842881 (ISBN) ; Afshin, H ; Baghaer Poor, A ; Sharif University of Technology
2007
Abstract
The present study investigates the turbulence characteristic of density current experimentally. The 3D Acoustic-Doppler Velocimeter (ADV) was used to measure the instantaneous velocity and characteristics of the turbulent flow. The courses of experiment were conducted in a three-dimensional channel for different discharge flows, concentrations, and bed slopes. Results are expressed at various distances from the inlet, for all flow rates, slopes and concentrations as the distribution of turbulence energy, Reynolds stress and the turbulent intensity. It was concluded that the maximum turbulence intensity happens in both the interface and near the wall. Also it was observed that turbulence...
3-D simulation of turbulent density
, Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) ; Firoozabadi, B ; Afshin, H ; Ghasvari Jahromi, H ; Sharif University of Technology
2006
Abstract
Density current is a dense fluid, which is continuously released from a source and spreads down a sloping surface inside a lighter, motionless fluid. A low-Reynolds number k-ε model (Launder and Sharma, 1974) has been used to simulate the behavior of 3-D density currents. Density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been verified with the experimental data sets. Although the k-ε Launder and Sharma model is applied here to a conservative density current, it seems the analysis is valid in general for turbidity current laden with fine particles. Copyright © 2006 by ASME
Analytical solution of turbulent couette flow by cosserat continuum model and gradient theory
, Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) ; Atefi, Gh ; Moosaie, A ; Hormozi, S ; Afshin, H ; Sharif University of Technology
2006
Abstract
In present paper the theory of the micropolar fluid based on a Cosserat continuum model has been applied for analysis of Couette flow. The obtained results for the velocity field have been compared with known results from experiments done by Reichardt at Max Plank institute for fluids in Gottingen [1,2] and analytical solution of the problem from Gradient theory by alizadeh[3].the boundary condition used here was the no slip one and Trostel's slip boundary condition[4].a good agreement between experimental results and the results of the problem for Reynolds near 18000 has beeen found. A new dimensionless number introduced that indicates the theoretical relation between cosserat theory and...
Comparison of 2_D turbulent particle laden density current and wall jets
, Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) ; Firoozabadi, B ; Ghasvari Jahromi, H ; Afshin, H ; Sharif University of Technology
2006
Abstract
Dense underflows are continuous currents, which move down the slope due to the fact that, their density are heavier than ambient water. In turbidity currents the density differences arises from suspended solids. Vicinity of the wall make density currents and wall jets similar in some sense but Variation of density cause this flows more complex than wall jets. An improved form of 'near-wall' k-ε turbulence model is chosen which preserve all characteristics of both density and wall jet currents and a compression is made between them. Then the outcomes from low Reynolds number k-ε model is compared with v2̄-f model which show similarity. Also results show good agreement with experimental data...
Computation of three-dimensional supersonic turbulent flows over wrap-around fin projectiles using personal computers
, Article Scientia Iranica ; Volume 12, Issue 2 , 2005 , Pages 217-228 ; 10263098 (ISSN) ; Azimi, A ; Farhanieh, B ; Sharif University of Technology
Sharif University of Technology
2005
Abstract
The three-dimensional supersonic turbulent flows over wrap-around fin missiles have been computed using the Thin Layer Navier-Stokes (TLNS) equations to reduce the computational efforts compared to those of the Full Navier-Stokes (FNS) equations. In this research, the missile configuration is divided into multi regions to enable fluid flow simulation using Personal Computers (PC). It also makes it possible to use a different number of nodes and distribution of grids in each region to enhance the accuracy. The Thin Layer Navier-Stokes equations in the generalized coordinate system were solved using an efficient, implicit, finite-difference factored algorithm of the Beam and Warming. For the...
Numerical Simulation of Dynamic Stall of Consecutive Wind Turbine Blades' Airfoil
, M.Sc. Thesis Sharif University of Technology ; Taeibi-Rahni, Mohammad (Supervisor)
Abstract
Today energy sources, in any kind, have their special situation in human’s life and we must use our knowledge to manage them for effective usage by decreasing losses and finding modern renewable sources. One of the best way to achieve this purpose is increasing efficiency and improve energy generator performances under different environmental conditions. In spite of the fact that wind turbines stall dynamics behavior is under investigation for 6 years, study of dynamic stall phenomenon especially over series blades still needed. By addition to this phenomenon, improper wind turbine arrange decreases efficiency too. As a matter of fact, scrutiny of dynamics stall of wind turbines serial...
Investigation of bed Stability in Downstream for the Diversion dam under Scour (Mill & Moghan case study)
, M.Sc. Thesis Sharif University of Technology ; Shamsai, Abolfazl (Supervisor)
Abstract
Numerical simulations and large eddy simulations (LES) of turbulent flow downstream of diversion dam , pool-riffle bedform in different geometrical ratios (different lengths of riffle and pool) with flow Reynolds number of 3.0 E+04 to 3.3E+04, downstream of special case study "Mill and Moghan diversion dam" with Froude number of 0.5 are presented The calculations are performed using a computational fluid dynamics model, FLOW-3D, which solves the Navier-Stokes equations in three dimensions with finite volume method. Numerical simulations are validated by comparing the numerical results of time-averaged flow patterns downstream of pool-riffle sequence with that of the experimental...
Numerical Simulation of Turbulent Flow Heat Transfer in the Entrance Region of Microchannels
, M.Sc. Thesis Sharif University of Technology ; Nouri Borujerdi, Ali (Supervisor)
Abstract
In this thesis the steady state convective heat transfer for turbulent, two-dimensional, incompressible gas flow in a circular microchannel under slip flow and temperature jump conditions is numerically investigated by means of finite volume scheme. The low Reynolds number k-ε turbulence model is employed using a new boundary condition for turbulent kinetic energy at solid surface. To calculate variables at control volume surfaces in the axial direction upwind differencing scheme and in the radial direction central differencing scheme are used. Rhie-Chow interpolation technique is used to prevent pressure field oscillations. The set of discrete equations are solved using SIMPLE Algorithm. In...
Numerical analysis of the swirl intensity decay rate for internal turbulent swirling flow
, Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 1 SYMPOSIA, Issue PART B , August , 2007 , Pages 1987-1995 ; 0791842886 (ISBN); 9780791842881 (ISBN) ; Mousavian, S. M ; Saidi, M. H ; Sharif University of Technology
2007
Abstract
In this research the trend of swirl decay and factors influencing the turbulent swirl flows have been investigated in a fixed pipe. In this regard, turbulent swirling decay flow with solid body rotation has been numerically surveyed using different flow conditions at the pipe inlet. The numerical results have been validated and compared with the existing mathematical relations having satisfactory agreement. Results show that the swirl intensity decay rate has strong dependency on the Reynolds number. On this basis, correlations have been proposed which improves predictions of swirl intensity decay rate at upstream regions and those with high swirl intensity. In addition, analyses have been...
Effects of reduced frequency on the performance of a wind turbine blade in the low and high turbulent unsteady flow
, Article 25th AIAA Applied Aerodynamics Conference, 2007, Miami, FL, 25 June 2007 through 28 June 2007 ; Volume 2 , 2007 , Pages 877-882 ; 10485953 (ISSN); 1563478986 (ISBN); 9781563478987 (ISBN) ; Amiralaei, M. R ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2007
Abstract
An extensive experimental study is conducted to investigate the effects of reduced frequency on a harmonically pitching wing where its cross section is used in a 660 kW wind turbine under construction in Iran. The corresponding lift coefficient and real time pressure signatures at three sections of the model at various reduced frequencies are examined. The test covers a wide range of angles of attack at prestall, stall, and deep stall regions. Pressure distributions at tip, middle, and root sections of the wing were recorded and from these distributions the lift coefficients are computed. The results show great role of the reduced frequency in altering the maximum lift coefficients, lift...
Computation of turbulent flow over highly curved configuration using a conventional two-equation turbulence model
, Article 45th AIAA Aerospace Sciences Meeting 2007, Reno, NV, 8 January 2007 through 11 January 2007 ; Volume 9 , 2007 , Pages 6262-6275 ; 1563478900 (ISBN); 9781563478901 (ISBN) ; Taeibi Rahni, M ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2007
Abstract
A new procedure for simulating turbulent flow in three-dimensional arbitrary geometries is presented. Finite volume method using physical covariant velocities on a staggered grid arrangement was used in this investigation. This work is an extension of previous successful work to three-dimensional cases. The ability of the new algorithm was tested using a conventional two-equation turbulence model on a highly separated turbulent flow test case. The low Reynolds number k-ω turbulence model of Wilcox was utilized to evaluate its capability in modeling highly curved flows. Turbulent flow over a three-dimensional hill, which is appropriate in assessment of ability of turbulence models in...
Firm structure of the separated turbulent shear layer behind modified backward-facing step geometries
, Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 16, Issue 7 , 2006 , Pages 803-826 ; 09615539 (ISSN) ; Taeibi Rahni, M ; Naderi, A.R ; Sharif University of Technology
2006
Abstract
Purpose - One major challenge in turbulent flow applications is to control the recirculation zone behind the backward-facing step (BFS). One simple idea to do so is to modify the original BFS geometry, of course, without causing adverse or undesirable impacts on the original characteristics of the primary stream. The main objective of this work is to examine the solidity of the recirculation zone behind several different geometries which are slightly to moderately different from the original BFS geometry. Design/methodology/approach - The implemented modifications cause complicated irregularities at the boundaries of the domain. The experience shows that the mesh distribution around these...
Analytical solution of turbulent problems using governing equation of cosserat continuum model
, Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 08888116 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) ; Atefi, Gh ; Moosaie, A ; Hormozi, S ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2006
Abstract
In present paper the theory of the micropolar fluid based on a Cosserat continuum model has been applied for analysis of Couette flow and turbulent flow through rough pipes. The obtained results for the velocity field have been compared with known results from experiments done by Reichardt at Max Plank institute for fluids in Gottingen [1,2] and analytical solution of the problem from Gradient theory by alizadeh[3] for couette problem and with known results from experiments done by Nikuradse (1932).the boundary condition used here was the no slip one and Trostel's slip boundary condition[4].a good agreement between experimental results and the results of the problem for Reynolds near 18000...
Comparison of 2-D turbulent particle laden density current and wall jets
, Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 1 SYPMOSIA , 2006 , Pages 1763-1770 ; 0791847500 (ISBN); 9780791847503 (ISBN) ; Firoozabadi, B ; Ghasvari Jahromi, H ; Afshin, H ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
Dense underflows are continuous currents, which move down the slope due to the fact that, their density are heavier than ambient water. In turbidity currents the density differences arises from suspended solids. Vicinity of the wall make density currents and wall jets similar in some sense but Variation of density cause this flows more complex than wall jets. An improved form of 'near-wall' k-ε turbulence model is chosen which preserve all characteristics of both density and wall jet currents and a compression is made between them. Then the outcomes from low Reynolds number k-ε model is compared with v̄2 - f model which show similarity. Also results show good agreement with experimental data...
3-D simulation of turbulent density
, Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2 FORUMS , 2006 , Pages 361-367 ; 0791847500 (ISBN); 9780791847503 (ISBN) ; Firoozabadi, B ; Ghasvari Jahromi, H ; Afshin, H ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
Density current is a dense fluid, which is continuously released from a source and spreads down a sloping surface inside a lighter, motionless fluid. A low-Reynolds number k-ε model (Launder and Sharma, 1974) has been used to simulate the behavior of 3-D density currents. Density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been verified with the experimental data sets. Although the k-ε Launder and Sharma model is applied here to a conservative density current, it seems the analysis is valid in general for turbidity current laden with fine particles. Copyright © 2006 by ASME
Numerical simulation of buoyancy affected turbulent air flow in a room
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Fathi Gishnegani, A ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
In this paper a three-dimensional steady state incompressible turbulent air flow is considered in a large single room. The buoyancy affected turbulent air flow is simulated by solving governing equations numerically. The turbulence modeling includes both k - ε and zero-equation models and their results are compared to the experimental data. The paper reviews several aspects such as displacement of radiator system performance, temperature and flow field distribution and comfort. The results show that the best temperature distribution and comfort obtain when radiator is installed under the window and its height be equal to or greater than that of the window. Copyright © 2006 by ASME