Experimental investigation on the influence of boundary layer thickness on the base pressure and near-wake flow features of an axisymmetric blunt-based body

2013 ◽  
Vol 54 (11) ◽  
Author(s):  
Alessandro Mariotti ◽  
Guido Buresti
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Base Pressure ◽  
Wake Flow ◽  
Near Wake ◽  
Flow Features

Boundary Layer Closure and Heat Transfer in Constant Base Pressure and Simple Wave Guns

1978 ◽  
Vol 100 (4) ◽  
pp. 690-696 ◽  
Author(s):  
A. D. Anderson ◽  
T. J. Dahm
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Method Of Characteristics ◽  
Simple Wave ◽  
Momentum Equation ◽  
Base Pressure ◽  
Two Dimensional ◽  
The Method Of Characteristics

Solutions of the two-dimensional, unsteady integral momentum equation are obtained via the method of characteristics for two limiting modes of light gas launcher operation, the “constant base pressure gun” and the “simple wave gun”. Example predictions of boundary layer thickness and heat transfer are presented for a particular 1 in. hydrogen gun operated in each of these modes. Results for the constant base pressure gun are also presented in an approximate, more general form.

Boundary-layer thickness and base pressure

AIAA Journal ◽  
1985 ◽  
Vol 23 (12) ◽  
pp. 1987-1989 ◽  
Author(s):  
Mauri Tanner
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Base Pressure

Coolant Jets Interaction in Effusion Cooling System: Experimental and Numerical Study

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Y. Jiang ◽  
A. V. Murray ◽  
P.T. Ireland ◽  
L. di Mare
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Cooling System ◽  
Numerical Study ◽  
Mesh Size ◽  
Cooling Flow ◽  
Fine Mesh ◽  
Flow Features ◽  
Single Jet

Abstract The interaction of coolant jets is significant in effusion settings as a result of the short streamwise and spanwise distance between films. This complicates the design of effusion cooling devices because computing the interaction between numerous, closely spaced rows of films is a challenging task. A flat plate effusion cooling model is investigated at both low and high blowing ratios. Pressure-sensitive paint (PSP) is used to measure film effectiveness. Computational fluid dynamics (CFD) calculations are performed to examine the cooling flow features in detail. The mesh sensitivity is studied to demonstrate the effect of mesh size on film effectiveness. The solution obtained by coarse mesh may not capture the correct trend with blowing ratio variation. Results of the computational work by fine mesh demonstrate good agreement with the measured effectiveness. Coolant jets interaction is also investigated. The profile of quantities such as velocity, temperature, kinetic energy, and Reynolds stress at several locations in the flow field is compared. The boundary layer profiles are scaled by the thermal boundary layer thickness to study the feature of heat transfer. It is observed that profiles of the flow quantities are self-similar. Two distinct scalings are found: an outer scaling based on boundary layer thickness which collapses the upper part of the profiles; an inner scaling which collapses the profiles at distances from the wall comparable to the penetration depth of a single jet. The latter scaling is based on the distance from the wall to the minimum temperature profile. This distance identifies the location of the coolant leaving the effusion cooling device.

Turbulence Amplification in Flow About an Airfoil

1980 ◽  
Author(s):  
W. Z. Sadeh ◽  
P. P. Sullivan
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Background Level ◽  
Turbulent Energy ◽  
Stagnation Zone ◽  
Stagnation Flow ◽  
Flow Situation ◽  
Stretching Effect

An experimental investigation of the evolution of freestream turbulence in flow about an airfoil was conducted in order to ascertain its selective amplification induced by the stretching mechanism according to the vorticity-amplification theory. Significant amplification of the streamwise turbulent energy transpired even in the limiting flow situation studied of a symmetric airfoil at zero angle of attack where the stretching is the least. Substantiation of the stretching effect was provided by the almost 100 percent amplification of turbulence with respect to its background level in the absence of the airfoil. Realization of preferred amplification at scales larger than the neutral scale of the stagnation flow was clearly indicated by the variation of the discrete streamwise turbulent energy. Particularly important was the detection of a most amplified scale which is characteristic of the coherent substructure near the airfoil stagnation zone and, concurrently, commensurate with the boundary-layer thickness.

Characteristics of the Flow Past a Wall-Mounted Finite-Length Square Cylinder at Low Reynolds Number With Varying Boundary Layer Thickness

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Sachidananda Behera ◽  
Arun K. Saha
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Flow Field ◽  
Layer Thickness ◽  
Finite Length ◽  
Boundary Layer Thickness ◽  
Square Cylinder ◽  
Near Wake ◽  
Wall Boundary Layer ◽  
Wall Boundary

Direct numerical simulation (DNS) is performed to investigate the modes of shedding of the wake of a wall-mounted finite-length square cylinder with an aspect ratio (AR) of 7 for six different boundary layer thicknesses (0.0–0.30) at a Reynolds number of 250. For all the cases of wall boundary layer considered in this study, two modes of shedding, namely, anti-symmetric and symmetric modes of shedding, were found to coexist in the cylinder wake with symmetric one occurring intermittently for smaller time duration. The phase-averaged flow field revealed that the symmetric modes of shedding occur only during instances when the near wake experiences the maximum strength of upwash/downwash flow. The boundary layer thickness seems to have a significant effect on the area of dominance of both downwash and upwash flow in instantaneous and time-averaged flow field. It is observed that the near-wake topology and the total drag force acting on the cylinder are significantly affected by the bottom-wall boundary layer thickness. The overall drag coefficient is found to decrease with thickening of the wall boundary layer thickness.

Effect of Free-Stream Velocity Definition on Boundary Layer Thickness and Losses in Centrifugal Compressors

2017 ◽  
Author(s):  
Jonna Tiainen ◽  
Ahti Jaatinen-Värri ◽  
Aki Grönman ◽  
Teemu Turunen-Saaresti ◽  
Jari Backman
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Centrifugal Compressor ◽  
Boundary Layer Thickness ◽  
Free Stream ◽  
Compressor Blade ◽  
Free Stream Velocity ◽  
Wake Flow ◽  
Stream Velocity ◽  
Centrifugal Compressors

The estimation of boundary layer losses requires the accurate specification of the free-stream velocity, which is not straightforward in centrifugal compressor blade passages. This challenge stems from the jet-wake flow structure, where the free-stream velocity between the blades cannot be clearly specified. In addition, the relative velocity decreases due to adverse pressure gradient. Therefore, the common assumption of a single free-stream velocity over the blade surface might not be valid in centrifugal compressors. Generally in turbomachinery, the losses in the blade cascade boundary layers are estimated e.g. with different loss co-efficients, but they often rely on the assumption of a uniform flow field between the blades. To give guidelines for the estimation of the mentioned losses in highly distorted centrifugal compressor flow fields, this paper discusses the difficulties in the calculation of the boundary layer thickness in the compressor blade passages, compares different free-stream velocity definitions, and demonstrates their effect on estimated boundary layer losses. Additionally, a hybrid method is proposed to overcome the challenges of defining a boundary layer in centrifugal compressors.

Coolant Jets Interaction in Effusion Cooling System: Experimental and Numerical Study

2019 ◽  
Author(s):  
Y. Jiang ◽  
A. V. Murray ◽  
P. T. Ireland ◽  
L. di Mare
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Cooling System ◽  
Numerical Study ◽  
Mesh Size ◽  
Cooling Flow ◽  
Fine Mesh ◽  
Flow Features ◽  
Single Jet

Abstract The interaction of coolant jets is significant in effusion settings as a result of the short streamwise and spanwise distance between films. This complicates the design of effusion cooling devices because computing the interaction between numerous, closely spaced rows of films is a challenging task. A flat plate effusion cooling model is investigated at both low and high blowing ratios. Pressure sensitive paint (PSP) is used to measure film effectiveness. Computational fluid dynamics (CFD) calculations are performed to examine the cooling flow features in detail. The mesh sensitivity is studied to demonstrate the effect of mesh size on film effectiveness. The solution obtained by coarse mesh may not capture the correct trend with blowing ratio variation. Results of the computational work by fine mesh demonstrate good agreement with the measured effectiveness. Coolant jets interaction is also investigated. The profile of quantities such as velocity, temperature, kinetic energy and Reynolds stress at several locations in the flow field is compared. The boundary layer profiles are scaled by the thermal boundary layer thickness to study the feature of heat transfer. It is observed that profiles of the flow quantities are self-similar. Two distinct scalings are found: an outer scaling based on boundary layer thickness which collapses the upper part of the profiles; an inner scaling which collapses the profiles at distances from the wall comparable to the penetration depth of a single jet. The latter scaling is based on the distance from the wall to the minimum temperature profile. This distance identifies the location of the coolant leaving the effusion cooling device.

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