AN EXPERIMENTAL STUDY OF THE EFFECTS OF BOUNDARY LAYER THICKNESS AND VELOCITY PROFILE ON THE PRESSURE DISTRIBUTIONS OF OBJECTS IMMERSED IN THE BOUNDARY LAYER

1965 ◽  
Author(s):  
Jr. Sayre ◽  
Clifford L.
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Velocity Profile ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Pressure Distributions

Magnetohydrodynamics Williamson Fluid Comprising Gyrotactic Microorganisms Flows Through a Permeable Stretching Layer with Variable Fluid Properties

2020 ◽  
Vol 9 (4) ◽  
pp. 375-387
Author(s):  
Amit Parmar ◽  
Rakesh Choudhary ◽  
Krishna Agarwal
Keyword(s):  
Boundary Layer ◽  
Velocity Profile ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Schmidt Number ◽  
Gyrotactic Microorganisms ◽  
Williamson Fluid ◽  
Non Linear ◽  
Fluid Properties ◽  
Variable Prandtl Number

The present study shows the impacts of Williamson fluid with magnetohydrodynamics flow containing gyrotactic microorganisms under the variable fluid property past permeable stretching sheet. Variable Prandtl number, mass Schmidt number, and gyrotactic microorganisms Schmidt number were all considered. The momentum, energy, mass, and microorganism equations’ governing PDEs are converted into nonlinear coupled ODEs and numerically solved with the bvp4c solver using suitable transformations. The main outcome of this study is that Williamson fluid parameter constantly decreases in velocity profile, however reverse effects can be shown in temperature profile. Also, M parameter and Kp parameter enhance the heat transfer rate, concentration rate and microorganisms boundary layer thickness but declines in momentum boundary layer thickness and velocity profile. The aim of this research is to see how velocity slide, temperature jump, concentration slip, and microorganism slip affect MHD Williamson fluid flow with gyrotactic microorganisms over a leaky surface embedded in spongy medium, with non-linear radiation and non-linear chemical reaction.

Melting heat transfer in the stagnation-point flow of Maxwell fluid with double-diffusive convection

2014 ◽  
Vol 24 (3) ◽  
pp. 760-774 ◽  
Author(s):  
Tasawar Hayat ◽  
Muhammad Farooq ◽  
Ahmad Alsaedi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Velocity Profile ◽  
Layer Thickness ◽  
Stagnation Point ◽  
Boundary Layer Thickness ◽  
Double Diffusive Convection ◽  
Content Type ◽  
Diffusive Convection ◽  
Double Diffusive

Purpose – The purpose of this paper is to analyze the melting heat transfer in the stagnation-point flow with double-diffusive convection. Design/methodology/approach – Series solutions for velocity, temperature and concentration are constructed via homotopy analysis method. Findings – The authors observed that the behaviors of N, ?2 and M on the velocity and boundary layer thickness are qualitatively similar. Further, for A<1 the velocity profile and boundary layer thickness increase with the increase of A. However, when A>1 then the velocity profile increases but the boundary layer thickness decreases when A is increased. Originality/value – This analysis has not been discussed in the literature previously.

Effect of velocity profile on instability of the viscoelastic liquid sheet

2014 ◽  
Vol 229 (11) ◽  
pp. 2031-2044 ◽  
Author(s):  
Runze Duan ◽  
Zhiying Chen ◽  
Liansheng Liu
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Velocity Profile ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Liquid Sheet ◽  
Viscoelastic Liquid ◽  
Rheological Parameters ◽  
Liquid Sheets ◽  
Elasticity Number

A linear analysis method has been used to investigate the instability behavior of the viscoelastic liquid sheets moving in the surrounding ambient gas. The gas boundary layer thickness and the liquid sheet velocity profile were taken into account. The effects of gas and liquid viscosity on the growth rate were revealed. The governing equations were obtained through analysis of the liquid and gas domain and solved using the spectral method. The viscoelastic rheological parameters and some flow parameters have been tested to investigate their influences on the instability of the viscoelastic liquid sheets. The results reveal that the disturbances grow faster for the viscoelastic liquid sheet than Newtonian one with identical viscosity. Moreover, the increases of Weber number, elasticity number, gas Reynolds number, and momentum flux ratio can accelerate the breakup of the viscoelastic liquid sheet. However, the increases of time constant ratio, boundary layer thickness, and liquid Reynolds number have the opposite effects.

A Second Turbulent Regime When a Fully Developed Axial Turbulent Flow Enters a Rotating Pipe

2016 ◽  
Author(s):  
Ferdinand-J. Cloos ◽  
Anna-L. Zimmermann ◽  
Peter F. Pelz
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Circumferential Velocity ◽  
Turbulent Regime ◽  
Self Similarity ◽  
Flow Number

When a fluid enters a rotating circular pipe a swirl boundary layer with thickness of δ̃s appears at the wall and interacts with the axial momentum boundary layer with thickness of δ̃. We investigate a turbulent flow applying Laser-Doppler-Anemometry to measure the circumferential velocity profile at the inlet of the rotating pipe. The measured swirl boundary layer thickness follows a power law taking Reynolds number and flow number into account. A combination of high Reynolds number, high flow number and axial position causes a transition of the swirl boundary layer development in the turbulent regime. At this combination, the swirl boundary layer thickness as well as the turbulence intensity increase and the latter yields a self-similarity. The circumferential velocity profile changes to a new presented self-similarity as well. We define the transition inlet length, where the transition appears and a stability map for the two regimes is given for the case of a fully developed axial turbulent flow enters the rotating pipe.

scholarly journals Turbulent theory of velocity-profile-induced jet breakup

2019 ◽  
Author(s):  
Ben Trettel
Keyword(s):  
Boundary Layer ◽  
Velocity Profile ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Turbulent Jets ◽  
Velocity Profiles ◽  
Common Belief ◽  
Integral Scale ◽  
Nozzle Length ◽  
Jet Breakup

Velocity profile relaxation is commonly believed to be a cause of jet breakup. This claim is critically reevaluated in this work. Contrary to common belief, laminar liquid jets with parabolic velocity profiles are actually more stable than laminar jets with flatter velocity profiles. This is shown using prior theory and experiments. For turbulent jets, the influence of the velocity profile is more difficult to determine. Previous experimentalists claimed to show that the velocity profile has an effect by varying the nozzle length. The claim is that the boundary layer thickness grows with nozzle length, and that the larger the boundary layer, the less stable the jet. In this work, nozzle length is shown to be a poor proxy for velocity profile effects because the turbulence intensity also increases as the nozzle length increases. Studies with this confounding were ignored in this work. Thinner boundary layers have greater shear, yet experiments have shown that if the boundary layer were made thinner (all else constant), the jet often is more stable. This is termed the "shear paradox". A potential resolution to the shear paradox is developed by considering that the area with shear also decreases as the boundary layer thickness is decreased, and by non-dimensionalizing the turbulent production rate by the dissipation. This theory shows an interaction between the integral scale and velocity profile relaxation which has not been previously discussed. The theoretical prediction that a smaller integral scale leads to more stable jets (due to increased turbulent dissipation) is shown to be somewhat consistent with the limited experimental and DNS data available.

Effect of Endwall Boundary Layer Thickness on Losses in a LPT Cascade With Unsteady Wakes

2014 ◽  
Author(s):  
Anika Steurer ◽  
Stuart I. Benton ◽  
Jeffrey P. Bons
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
High Lift ◽  
Time Resolved ◽  
Low Pressure Turbine ◽  
Pressure Distributions ◽  
Wake Passing ◽  
Different Thickness

The effects of inlet endwall boundary layer thickness and up-stream unsteady wakes are investigated experimentally in a low-speed linear cascade. The examined airfoil is the front-loaded L2F, a high-lift low-pressure turbine profile with high resistance to separation even in the low Reynolds number regime. Cases are documented with and without incoming wakes for two inlet endwall boundary layers of different thickness at a Reynolds number of Re = 30,000. Periodic incoming wakes are simulated with moving bars upstream of the cascade. The inlet endwall boundary layer is conditioned with a two-part splitter plate, one part downstream and one part upstream of the wake generator. By the documentation of pressure distributions on the blades, velocity profiles in the cascade inlet as well as total pressure loss and phase-locked velocity data in the outlet, this work attempts to show that varying the inlet endwall boundary layer thickness combined with the effect of incoming wakes has significant influence on the performance of blades with relatively low aspect ratio in cascade experiments. Depending on boundary layer thickness, wakes are shown to have either a stronger impact on midspan or on endwall performance. Time-resolved velocity and vorticity plots additionally show the motion of the vortex and loss core at the blade trailing edge during the event of wake passing.

Experimental Study of Surface Roughness Effects on a Turbine Airfoil in a Linear Cascade— Part II: Aerodynamic Losses

2011 ◽  
Vol 134 (4) ◽  
Author(s):  
M. Lorenz ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Experimental Study ◽  
Surface Roughness ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Roughness Effects ◽  
Aerodynamic Losses

The present experimental study is part of a comprehensive analysis accounting for heat transfer and aerodynamic losses on a highly loaded low pressure turbine blade with varying surface roughness. Whereas Part I focuses on heat transfer measurements at airfoil midspan with different deterministic surface roughnesses, Part II investigates surface roughness effects on aerodynamic losses of the same airfoil. A set of different arrays of deterministic roughness (the same as used in Part I) is investigated in these experiments. The height and eccentricity of the roughness elements are varied, showing the combined influence of roughness height and anisotropy on the losses produced in the boundary layers. It is shown that the boundary layer loss is dominated by the suction side. Therefore, the investigations focus on measurements of the suction side boundary layer thickness at midspan directly upstream of the trailing edge. The experiments are conducted at several freestream turbulence levels (Tu1=1.4–10.1%) and different Reynolds numbers. The measurements reveal that suction side boundary layer thickness is increased by up to 190% if surface roughness shifts the transition onset upstream. However, in some cases, at low Reynolds numbers and freestream turbulence, surface roughness suppresses boundary layer separation and decreases the trailing edge boundary layer thickness by up to 30%.

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