Three-dimensional numerical modeling of flow upstream of a symmetric streamlined body mounted over a flat plate with tip gap

2022 ◽  
pp. 095440622110470
Author(s):  
Ovais U Khan ◽  
Ghulam Arshed ◽  
Mohammad Javed Khan
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Numerical Simulations ◽  
Flat Plate ◽  
Free Stream ◽  
Three Dimensional ◽  
System Structure ◽  
Research Activity ◽  
Vortex System ◽  
Streamlined Body

In this research activity numerical simulations are carried out to investigate the flow field upstream of a symmetric streamlined body mounted perpendicular to a flat plate with and without clearance gap between the tip of the streamlined body and the flat plate with laminar boundary layer. The developed numerical model successfully predicted the three-dimensional horseshoe vortex system upstream of the streamlined body with and without the tip gap. The resulting vortex system for the configuration with tip gap contains multiple vortices with characteristics similar to that of end-wall-flows of surface-mounted obstacles. The effects of varying tip gap clearance for various values of free stream Reynolds number are also investigated. It was found that the introduction of a gap between the streamlined body tip and flat surface caused shifting of the vortex structure system in the upstream direction. Moreover, it is observed that the free stream Reynolds number and the tip gap between the streamlined body and the flat plate substantially influences the unsteady character of the flow field and the vortex system structure. Results obtained from the numerical simulations are compared with experimental measurements of a blunt body configuration and have been found in good agreement.

Velocity Measurements Around Film Cooling Holes With Deposition

2010 ◽  
Author(s):  
Kristian Haase ◽  
Jeffrey P. Bons
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Flat Plate ◽  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Leading Edge ◽  
Flow Structures ◽  
Particle Image Velocimetry Technique ◽  
Film Cooling Holes

The choice of synthetic fuels (synfuels) in order to achieve greater fuel flexibility may lead to unwanted solid depositions on the blades of turbomachines. The objective of this paper is to gain information of the flow field over a turbine blade with depositions around the film cooling holes. For the investigation the particle image velocimetry technique (PIV) is utilized. The experiments are conducted in a low speed wind tunnel at a Reynolds number of 300,000 based on the distance from the leading edge to the middle of the cooling holes and a Reynolds number of 9,200 based on the hole diameter. Three different simulation plates are tested in the tunnel—a flat plate for comparison, a plate with large depositions only upstream of the holes, and one with smaller depositions all around the holes. The two deposition configurations are scaled models of actual depositions formed at simulated engine flow conditions on a turbine test coupon. The experiments are conducted at four different coolant to free stream blowing ratios—0, 0.5, 1, and 2—and at a density ratio of 1.1. PIV images are taken in four planes from the side of the tunnel to record the main flow structures and in five planes from the end of the tunnel to record the secondary flow structures. The results show that the type of deposition has a large influence on the flow field. With the smaller depositions the penetration of the coolant jet into the free stream is significantly reduced but the dimension and strength of the kidney vortices is increased compared to the flat plate. With the large depositions, on the other hand, the penetration of the coolant jet is much higher due to the ramp effect and the dimension of the secondary vortices is also increased. It can also be seen that the coolant gathers and stays behind the large depositions and then flows off very slowly. Film effectiveness and surface heat flux data acquired with the same plates (and reported previously) allow the identification of flow features and their direct influence on the film cooling performance.

Dynamic Stall Simulation of Flow Over NACA0012 Airfoil at 1 Million Reynolds Number

2015 ◽  
Author(s):  
Venkata Ravishankar Kasibhotla ◽  
Danesh Tafti
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Dynamic Stall ◽  
Sharp Drop ◽  
Airfoil Surface ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Edge Vortex

The paper is concerned with the prediction and analysis of dynamic stall of flow past a pitching NACA0012 airfoil at 1 million Reynolds number based on the chord length of the airfoil and at reduced frequency of 0.25 in a three dimensional flow field. The turbulence in the flow field is resolved using large eddy simulations with the dynamic Smagorinsky model at the sub grid scale. The development of dynamic stall vortex, shedding and reattachment as predicted by the present study are discussed in detail. This study has shown that the downstroke phase of the pitching motion is strongly three dimensional and is highly complex, whereas the flow is practically two dimensional during the upstroke. The lift coefficient agrees well with the measurements during the upstroke. However, there are differences during the downstroke. The computed lift coefficient undergoes a sharp drop during the start of the downstroke as the convected leading edge vortex moves away from the airfoil surface. This is followed by a recovery of the lift coefficient with the formation of a secondary trailing edge vortex. While these dynamics are clearly reflected in the predicted lift coefficient, the experimental evolution of lift during the downstroke maintains a fairly smooth and monotonic decrease in the lift coefficient with no lift recovery. The simulations also show that the reattachment process of the stalled airfoil is completed before the start of the upstroke in the subsequent cycle due to the high reduced frequency of the pitching cycle.

Numerical simulations and analysis of the turbulent flow field in a practical gas turbine engine combustor

2021 ◽  
pp. 095765092110632
Author(s):  
Veeraraghava R Hasti ◽  
Prithwish Kundu ◽  
Sibendu Som ◽  
Jay P Gore
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Gas Turbine ◽  
Adaptive Mesh Refinement ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Turbulent Structures ◽  
Cut Cell ◽  
Turbulent Flow Field

The turbulent flow field in a practical gas turbine combustor is very complex because of the interactions between various flows resulting from components like multiple types of swirlers, dilution holes, and liner effusion cooling holes. Numerical simulations of flows in such complex combustor configurations are challenging. The challenges result from (a) the complexities of the interfaces between multiple three-dimensional shear layers, (b) the need for proper treatment of a large number of tiny effusion holes with multiple angles, and (c) the requirements for fast turnaround times in support of engineering design optimization. Both the Reynolds averaged Navier–Stokes simulation (RANS) and the large eddy simulation (LES) for the practical combustor geometry are considered. An autonomous meshing using the cut-cell Cartesian method and adaptive mesh refinement (AMR) is demonstrated for the first time to simulate the flow in a practical combustor geometry. The numerical studies include a set of computations of flows under a prescribed pressure drop across the passage of interest and another set of computations with all passages open with a specified total flow rate at the plenum inlet and the pressure at the exit. For both sets, the results of the RANS and the LES flow computations agree with each other and with the corresponding measurements. The results from the high-resolution LES simulations are utilized to gain fundamental insights into the complex turbulent flow field by examining the profiles of the velocity, the vorticity, and the turbulent kinetic energy. The dynamics of the turbulent structures are well captured in the results of the LES simulations.

Integrated Microcomputer-LDV Instrumentation for Studying Finite Wing Aerodynamics

1993 ◽  
Author(s):  
Abdollah Khodadoust
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Data Acquisition ◽  
Fiber Optic ◽  
Three Dimensional ◽  
Laser Doppler ◽  
Laser Doppler Velocimeter ◽  
Ice Accretion ◽  
Wing Model ◽  
Finite Wing

Abstract The effect of a simulated glaze ice accretion on the flow field of a three-dimensional wing is studied experimentally. A PC-based data acquisition and reduction system was used with a four-beam two-color fiber-optic laser Doppler velocimeter (LDV) to map the flow field along three spanwise cuts on the model. Results of the LDV measurements on the upper surface of the finite wing model without the simulated glaze ice accretion are presented for α = 0 degrees at Reynolds number of 1.5 million. Measurements on the centerline of the clean model compared favorably with theory.

Two- and Three-Dimensional Simulations of the Flow Around a Cylinder Fitted With Strakes

2012 ◽  
Author(s):  
Bruno S. Carmo ◽  
Rafael S. Gioria ◽  
Ivan Korkischko ◽  
Cesar M. Freire ◽  
Julio R. Meneghini
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Free Stream ◽  
Three Dimensional ◽  
The Body ◽  
Vortex Wake ◽  
Two Dimensional ◽  
Flow Around A Cylinder ◽  
Three Dimensional Simulations ◽  
Angle Of Rotation

Two- and three-dimensional simulations of the flow around straked cylinders are presented. For the two-dimensional simulations we used the Spectral/hp Element Method, and carried out simulations for five different angles of rotation of the cylinder with respect to the free stream. Fixed and elastically-mounted cylinders were tested, and the Reynolds number was kept constant and equal to 150. The results were compared to those obtained from the simulation of the flow around a bare cylinder under the same conditions. We observed that the two-dimensional strakes are not effective in suppressing the vibration of the cylinders, but also noticed that the responses were completely different even with a slight change in the angle of rotation of the body. The three-dimensional results showed that there are two mechanisms of suppression: the main one is the decrease in the vortex shedding correlation along the span, whilst a secondary one is the vortex wake formation farther downstream.

On High-Performance Airfoil at Very Low Reynolds Number

2016 ◽  
Vol 28 (3) ◽  
pp. 273-285
Author(s):  
Katsuya Hirata ◽  
◽  
Ryo Nozawa ◽  
Shogo Kondo ◽  
Kazuki Onishi ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
High Performance ◽  
Low Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Slow Flow ◽  
Low Reynolds Numbers ◽  
Low Reynolds

[abstFig src='/00280003/02.jpg' width=""300"" text='Iso-Q surfaces of very-slow flow past an iNACA0015' ] The airfoil is often used as the elemental device for flying/swimming robots, determining its basic performances. However, most of the aerodynamic characteristics of the airfoil have been investigated at Reynolds numbers Re’s more than 106. On the other hand, our knowledge is not enough in low Reynolds-number ranges, in spite of the recent miniaturisation of robots. In the present study, referring to our previous findings (Hirata et al., 2011), we numerically examine three kinds of high-performance airfoils proposed for very-low Reynolds numbers; namely, an iNACA0015 (the NACA0015 placed back to front), an FPBi (a flat plate blended with iNACA0015 as its upper half) and an FPBN (a flat plate blended with the NACA0015 as its upper half), in comparison with such basic airfoils as a NACA0015 and an FP (a flat plate), at a Reynolds number Re = 1.0 × 102 using two- and three-dimensional computations. As a result, the FPBi shows the best performance among the five kinds of airfoils.

Turbulence Measurements in the Corner Wall Jet

2014 ◽  
Author(s):  
Barrett Poole ◽  
Joseph W. Hall
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Wall Jet ◽  
Hot Wire ◽  
Turbulence Measurements ◽  
Vertical Growth ◽  
The Mean ◽  
Turbulent Flow Field

The corner wall jet is similar to the standard three-dimensional wall jet with the exception that one half of the surface has been rotated counter-clockwise by 90 degrees. The corner wall jet investigated here is formed using a long round pipe with a Reynolds number of 159,000. Contours of the mean and turbulent flow field were measured using hot-wire anemometry. The results indicate that the ratio of lateral to vertical growth in the corner wall jet is approximately half of that in a standard turbulent three-dimensional wall jet.

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