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Turbulent reduction in a wind tunnel using trip strip
, Article Proceedings of the ASME Heat Transfer/Fluids Engineering Summer Conference 2004, HT/FED 2004, Charlotte, NC, 11 July 2004 through 15 July 2004 ; Volume 1 , 2004 , Pages 827-832 ; Dehghan Manshadi, M ; Mirabdollahi, M. J ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2004
Abstract
In this investigation an intensive experimental study was conducted to study the flow quality in a test section of a low speed, V∞ = 10 - 100, closed return wind tunnel. An interesting result was obtained when a trip strip, a guitar wire with D= 1.14mm, was installed near the end of the contraction region. Addition of this trip wire resulted in a turbulent reduction almost at all speed ranges along the entire test section. Further, it smoothness the variation of turbulent intensity along the test section too. Velocity profiles along the tunnel wall at various speeds using a rake were measured with and without the trip wire. In addition, pressure contours at different location of the test...
Bohmian approach to spin-dependent time of arrival for particles in a uniform field and for particles passing through a barrier
, Article Journal of Physics A: Mathematical and Theoretical ; Volume 41, Issue 37 , 13 August , 2008 ; 17518113 (ISSN) ; Golshani, M ; Sharif University of Technology
2008
Abstract
The de Broglie-Bohm interpretation of quantum mechanics with and without spin-dependence is used to determine electron trajectories, arrival-time distribution of electrons and the mean arrival time of spin-1/2 particles (including electrons) in the presence of a uniform field and a barrier separately. The difference for the mean arrival times, which are calculated with different guidance equations, is examined versus mass of the arriving particle and versus group velocity of the arriving electron wave packet and also versus the width of the barrier. Numerical calculations show that these differences are of the order of 10-18-10-17 s. Another feature of the modified guidance law is that...
Dissipative vibrational model for chiral recognition in olfaction
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 3 , 2015 ; 15393755 (ISSN) ; Taher Ghahramani, F ; Shafiee, A ; Sharif University of Technology
American Physical Society
2015
Abstract
We examine the olfactory discrimination of left- and right-handed enantiomers of chiral odorants based on the odorant-mediated electron transport from a donor to an acceptor of the olfactory receptors embodied in a biological environment. The chiral odorant is effectively described by an asymmetric double-well potential whose minima are associated to the left- and right-handed enantiomers. The introduced asymmetry is considered an overall measure of chiral interactions. The biological environment is conveniently modeled as a bath of harmonic oscillators. The resulting spin-boson model is adapted by a polaron transformation to derive the corresponding Born-Markov master equation with which we...
Wind tunnel study of the effect zigzag tape on aerodynamics performance of a wind turbine airfoil
, Article Journal of Advanced Research in Fluid Mechanics and Thermal Sciences ; Volume 41, Issue 1 , 2018 , Pages 1-9 ; 22897879 (ISSN) ; Lazim, T.M ; Darbandi, M ; Sharif University of Technology
Penerbit Akademia Baru
2018
Abstract
A wind tunnel study was performed on the FFA-W-3-270 airfoil, which form a segment of a 1.25 MW wind turbine blade, to examine the effect of fixed roughness height and position using a zigzag tape boundary layer trip strip. Tests were conducted at a Reynolds number of 1×106 over a wide range of angles of attack. The zigzag tape, as an artificial roughness device, not only triggers a premature transition in the flow whereby laminar flow regimes change to turbulent, but also increases the momentum thickness of the turbulent boundary layer and change the airfoil camber. The 60° zigzag tape of 0.5 mm and 1 mm height was placed on the suction side of the airfoil at different chord wise locations....
Correction to: parametric study and working fluid selection of modified combined power and refrigeration cycles (MCPRCs) using low-temperature heat sources (Journal of the Brazilian Society of Mechanical Sciences and Engineering, (2018), 40, 1, (30), 10.1007/s40430-018-0971-5)
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 40, Issue 2 , February , 2018 ; 16785878 (ISSN) ; Ghaebi, H ; Sharif University of Technology
Springer Verlag
2018
Abstract
The original version of this article unfortunately contained a mistake. The affiliation of the second author was incorrect. The correct information is given below: Hadi Ghaebi, Department of Mechanical Engineering, Faculty of Engineering, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil, Iran. © 2018, The Brazilian Society of Mechanical Sciences and Engineering
RANS modelling of a NACA4412 wake using wind tunnel measurements
, Article Fluids ; Volume 7, Issue 5 , 2022 ; 23115521 (ISSN) ; Hajipour, M ; Mallor, F ; Örlü, R ; Vinuesa, R ; Schlatter, P ; Sharif University of Technology
MDPI
2022
Abstract
Wake analysis plays a significant role in wind-farm planning through the evaluation of losses and energy yield. Wind-tunnel tests for wake studies have high costs and are time-consuming. Therefore, computational fluid dynamics (CFD) emerges as an efficient alternative. An especially attractive approach is based on the solution of the Reynolds-averaged Navier–Stokes (RANS) equations with two-equation turbulence closure models. The validity of this approach and its inherent limitations, however, remain to be fully understood. To this end, detailed wind-tunnel experiments in the wake of a NACA4412 wing section profile are compared with CFD results. Two-and three-dimensional RANS simulations are...
3D numerical investigation of the effects of driving of the new mechanized tunnel on existing segmental linings and ground surface settlements - a case study: Shiraz metro line 2
, Article International Journal of Geotechnical Engineering ; 2020 ; Shivaei, S ; Sadaghiani, M. H ; Nikooee, E ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Subway metro systems are one of the most efficient modes of mass transportation, especially in heavily populated areas. A series of 3D Finite Element Analysis (FEA) has been carried out to investigate the interaction between mechanized twin tunnels excavated beneath the highly congested streets of Shiraz (Iran). Firstly, the reference numerical model has been verified using the measured data of surface settlement control pins. The effects of driving of the new closed shield tunnel on the evolution of stress fields in the existing segmental lining as well as the ground surface settlements in the reference numerical model have been then quantified. Lastly, the effects of influencing factors...
Effect of EPB tunnelling on surface settlement
, Article Annual Conference of the Canadian Society for Civil Engineering 2007: Where the Road Ends, Ingenuity Begins, Yellowknife, NT, 6 June 2007 through 9 June 2007 ; Volume 2 , 2007 , Pages 1003-1012 ; Aliari, Y ; Sharif University of Technology
2007
Abstract
Settlement is one of the most important effects of tunnelling. In order to minimize this effect, it is necessary to arrange for circumstances to keep the strain and stress state of undisturbed soil within a tight limit. To achieve this, it is common nowadays to use closed face pressurized shields such as EPB TBMs. In this type of shield, face stability and ground settlement control is maintained by pressurizing the tunnel face with adjustment of cutter head thrust and muck removal discharge. In this paper, numerical modeling of excavation of twin tunnels in Tabriz subway is addressed with respect to the effect of EPB tunnelling in settlement control. Settlement and lining thrust are...
3D numerical investigation of the effects of driving of the new mechanized tunnel on existing segmental linings and ground surface settlements - a case study: Shiraz metro line 2
, Article International Journal of Geotechnical Engineering ; Volume 16, Issue 7 , 2022 , Pages 878-889 ; 19386362 (ISSN) ; Shivaei, S ; Sadaghiani, M. H ; Nikooee, E ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
Subway metro systems are one of the most efficient modes of mass transportation, especially in heavily populated areas. A series of 3D Finite Element Analysis (FEA) has been carried out to investigate the interaction between mechanized twin tunnels excavated beneath the highly congested streets of Shiraz (Iran). Firstly, the reference numerical model has been verified using the measured data of surface settlement control pins. The effects of driving of the new closed shield tunnel on the evolution of stress fields in the existing segmental lining as well as the ground surface settlements in the reference numerical model have been then quantified. Lastly, the effects of influencing factors...
Steady flow quality assessment of a modified transonic wind tunnel
, Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 500-507 ; 10263098 (ISSN) ; Soltani, M. R ; Haghiri, A ; Sharif University of Technology
2013
Abstract
An existing operational trisonic wind tunnel is upgraded to improve its performance criterion in the transonic regime. In this research, the test section is modified according to the operational requirements of the various existing transonic wind tunnels. Several perforated walls are designed, manufactured, and installed on the top and bottom sides of the test section. The flow in the test section of the wind tunnel is surveyed for the empty condition prior to testing models. Once satisfactory results regarding the flow quality requirements in the test section under various conditions were achieved, a 2D model, NACA 0012, and a 3D standard model for the transonic wind tunnels, AGARD-B, are...
Experimental investigation on turbulence intensity reduction in subsonic wind tunnels
, Article Aerospace Science and Technology ; Volume 15, Issue 2 , 2011 , Pages 137-147 ; 12709638 (ISSN) ; Soltani, M. R ; Manshadi, M. D ; Sharif University of Technology
Abstract
Experiments are performed to evaluate the impact of trip wires on the turbulence intensity in a few low speed wind tunnels. Trip wires of different sizes are installed at different positions in the contraction section of four different wind tunnels and measurements are made at various free stream velocities. The results indicate that the pressure distributions are altered compared to the clean condition. Trip wires move the adverse pressure gradient toward the inlet of the contraction section. Consequently, the turbulence intensity in the test section of the wind tunnels is reduced and the flow uniformity is improved considerably. Frequency and statistical analysis are performed and the...
An experimental and numerical prediction of marine propeller noise under cavitating and non-cavitating conditions
, Article Brodogradnja ; Volume 66, Issue 2 , 2015 , Pages 29-45 ; 0007215X (ISSN) ; Mehdigholi, H ; Seif, M ; Yaakob, O ; Sharif University of Technology
Brodarski Institute
2015
Abstract
In this study, the hydrodynamics and noise prediction of a five blade marine propeller were analyzed through numerical and experimental methods under variety operational conditions. The hydrodynamics of the propeller was studied and the characteristic curves were presented in both numerical and experimental methods. Inception and development of sheet cavitation conditions are obtained in both numerical and experimental methods. The cavitation was started and developed by either increasing the propeller rotational speed in constant pressure or decreasing pressure, while the velocity was kept constant. Good agreements are observed between numerical and experimental results, qualitatively and...
Scanning tunneling spectroscopy of MoS2 monolayer in presence of ethanol gas
, Article Materials Research Express ; Volume 5, Issue 4 , April , 2018 ; 20531591 (ISSN) ; Iraji Zad, A ; Berahman, M ; Aghakhani Mahyari, F ; Hosseini Shokouh, S. H ; Sharif University of Technology
Institute of Physics Publishing
2018
Abstract
Due to high surface to volume ratio and tunable band gap, two dimensional (2D) layered materials such as MoS2, is good candidate for gas sensing applications. This research mainly focuses on variation of Density of States (DOS) of MoS2 monolayes caused by ethanol adsorption. The nanosheets are synthesized by liquid exfoliation, and then using Scanning Tunneling Spectroscopy (STS) and Density Functional Theory (DFT), local electronic characteristic such as DOS and band gap in non-vacuum condition are analyzed. The results show that ethanol adsorption enhances DOS and deform orbitals near the valence and conduction bands that increase transport of carriers on the sheet. © 2018 IOP Publishing...
A new investigation on tunnel pool fire phenomenon using CFD technique
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 37, Issue 2 , March and April , 2018 , Pages 171-182 ; 10219986 (ISSN) ; Bab, V ; Ahmadi Sabegh, M ; Sharif University of Technology
Iranian Journal of Chemistry and Chemical Engineering
2018
Abstract
In this study, the amount of generated pool fire, as a result of the release of chemicals in the case of an accident in tunnels, was simulated and the results were compared to the experimental data. At first, various amounts of spatial resolution (R*) were considered to compare the existing experimental data at different heights at the upstream, downstream and above the pool fire. The comparison studies showed that both numerical predictions and experimental measurements were, in general, comparable. Furthermore, FDS code was used to simulate the tunnel fire scenario for both cases of natural and forced ventilation. The grid using in the simulations is assessed by cells with the optimal...
Leggett-Garg inequality for a two-level system under decoherence
, Article Open Systems and Information Dynamics ; Volume 25, Issue 1 , 2018 ; 12301612 (ISSN) ; Shafiee, A ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2018
Abstract
We consider a macroscopic quantum system subjected to an asymmetric double-well potential in a harmonic environment. By using a time-dependent approach, we calculate tunnelling probabilities for the system which contain oscillation effects. To show how one can decide between quantum mechanics and the implications of macrorealism assumptions, a given form of Leggett-Garg inequality is considered. The violation of this inequality occurs for a broader range of the system-environment interactions, compared to previous results obtained for two-level systems. Assuming that the coupling strength between the system and the environment can be controlled with time, one can see the violation even for...
Power spectrum and FFT-based signal analysis in turbulence measurements
, Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 275-278 ; 2010376X (ISSN) ; Tamadonfar, P ; Soltani, M. R ; Ghorbanian, K ; Masdari, M ; Sharif University of Technology
2009
Abstract
In this research, the employment of an innovative but simple and cost effective method for turbulent reduction in a low speed wind tunnel is investigated and the effect of this turbulence reduction on the Power Spectrum and FFT-Based signals that obtained from Hot-wire Anemometry is studied. These terms represents the amount of power contained in the signals. Several situations are studied in this paper. One of these situations is when there are four screens in the settling chamber of the wind tunnel and after that by adding the trip strip in the contraction region of the wind tunnel the tests were repeated. In the next stage, three screens were removed from the settling chamber of the wind...
Analysis of separation control authority of DBD plasma actuator using hot-film sensor array
, Article Journal of Applied Fluid Mechanics ; Volume 14, Issue 5 , 2021 , Pages 1421-1435 ; 17353572 (ISSN) ; Maghrebi, M. J ; Soltani, M. R ; Sharif University of Technology
Isfahan University of Technology
2021
Abstract
The boundary-layer control authority of a DBD plasma actuator using surface mounted hot-film sensors is evaluated. Wind tunnel experiments on a wind-turbine blade section were established at a Reynolds number of 0.27 x 106. Aerodynamic performance of the wind-turbine blade section for both plasma-ON and plasma-OFF modes are evaluated using measurements made by both surface pressure and wake survey behind the model. Two distinct boundary-layer states are recognized. A state which occurs at the onset and in proximity of the deep stall, which is affected by the low-frequency instabilities of the separated flow. In this case, the steady actuation of plasma imparts local momentum on the nearby...
Numerical solution of transient flow in wind tunnels
, Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 1 , 2004 , Pages 921-927 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Ziaei Rad, M ; Sharif University of Technology
American Society of Mechanical Engineers
2004
Abstract
This paper deals with design and analysis of intermittent supersonic wind tunnels. System can be constructed by allowing air at atmospheric pressure to pass through a converging-diverging nozzle, a test section and a diffuser into a vacuum tank. The governing equations of compressible fluid flow have been solved numerically using flux vector splitting method to obtain running time under which it works at the design Mach number. The formulation has been tested on the theory of quasi one-dimensional compressible flow. The numerical results are in good agreement with the results of the theory
Neural network: A new prediction tool for estimating the aerodynamic behaivior of a pitching delta wing
, Article 21st AIAA Applied Aerodynamics Conference 2003, Orlando, FL, 23 June 2003 through 26 June 2003 ; 2003 ; 9781624100925 (ISBN) ; Sadati, N ; Davari, A. R ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2003
Abstract
In this paper, a new approach based on a Generalized Regression Neural Network (GRNN) has been proposed to predict the unsteady forces and moments on a 70° swept wing undergoing sinusoidal pitching motion. Extensive wind tunnel results were being used for training the network and for verification of the values predicted by this approach. The Generalized Regression Neural Network (GRNN) has been trained by the aforementioned experimental data and subsequently was used as a prediction tool to determine the unsteady longitudinal forces and moments of the pitching delta wing for various reduced frequencies. The results are in a good agreement with those determined by the previous experimental...
Study of Air Pollutant Dispersion in Closed Motor Way Space: Resalat Tunnel Case Study
,
M.Sc. Thesis
Sharif University of Technology
;
Vaziri, Manouchehr
(Supervisor)
Abstract
Concentrations of air pollutants emitted by motor vehicles in traffic tunnels, due to low access of tunnels to Open space increases rapidly. Increasing the tunnel pollutant concentration, decreases tunnel air quality level which is very dangerous for human health. Thus study of traffic tunnel air pollution concentration and dispersion is important for offering control strategies in these spaces. This investigation has been tried to study vehicular pollutants emission and dispersion inside traffic tunnel by data collection that involves traffic, meteorology and air pollutants characteristics in a urban tunnel. So data collection was carried out in the Resalat tunnel located in urban...