Research Article
An Explanation for the Existence of Stall Hysteresis
Issue:
Volume 10, Issue 1, June 2025
Pages:
1-10
Received:
20 November 2024
Accepted:
20 December 2024
Published:
10 February 2025
Abstract: An explanation of the mechanism for the difference in angle for separation and reattachment during stall on airfoils via potential flow and stall-prediction theories is proposed as follows: the reattachment angle of any given airfoil is the stall angle of the effective body which encompasses the physical body and its trailing viscous wake. Airfoil hysteresis exists, above certain Reynolds numbers, when the angle of attack increases beyond the catastrophic stall angle with the flow remaining separated until lowered below the stall angle of attack. The size of the hysteresis loop is determined by the difference in separation and reattachment angles. Within the clockwise hysteresis loop there exist two distinct airfoil geometries: the physical and the effective. The physical, or actual airfoil geometry, dominates the behavior of the pre-catastrophic lift. The much longer (relatively thinner) effective body dominates the hysteresis loop from catastrophic stall to reattachment, which is what the flow “sees” from the potential flow perspective. Wind tunnel tests were conducted at the United States Air Force Academy’s (USAFA’s) Sub-Sonic Wind Tunnel (SWT) where excellent agreement (less than half a degree) is found for all tests thus far.
Abstract: An explanation of the mechanism for the difference in angle for separation and reattachment during stall on airfoils via potential flow and stall-prediction theories is proposed as follows: the reattachment angle of any given airfoil is the stall angle of the effective body which encompasses the physical body and its trailing viscous wake. Airfoil ...
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Research Article
Hydromagnetic Boundary Layer Flow and Heat Migration of Dual Stratified Eyring-Powell Fluid
Simon Waswa Wekesa
,
Winfred Nduku Mutuku
Issue:
Volume 10, Issue 1, June 2025
Pages:
11-20
Received:
10 May 2025
Accepted:
28 May 2025
Published:
23 June 2025
DOI:
10.11648/j.fm.20251001.12
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Abstract: The Eyring-Powell liquid is a type of non-Newtonian fluid. The complex flow behavior makes it useful in a variety of industrial and engineering applications such as drug manufacturing, paint and in armor construction. Blood, starch, nail polish and honey are such examples. The viscosity of these fluid changes with the rate at which the fluid shears. The need for improved heat transport fluid for industrial processes necessitates this research. The existing fluid are outdated by the advance in technology of machines. This paper modifies the classic Navier-Stokes equations to better capture the unique features of these fluids. The effect of a dual-layer structure on heat transfer in the hydromagnetic flow of an Eyring-Powell fluid near a boundary is numerically investigated. The state variable technique is used to generate and linearize the governing nonlinear differential equations as well as the applicable boundary conditions. The predictor-corrector scheme is utilized to solve the equations by calling the ode113 solver in matlab as the bvp5c function is employed for analysis. The predictor makes the first approximation which is refined by the corrector. The findings, graphically depicted, demonstrate that fluid velocity, temperature, and other parameters decrease with increasing magnetic field intensity, thermal stratification, concentration stratification, and Nusselt number.
Abstract: The Eyring-Powell liquid is a type of non-Newtonian fluid. The complex flow behavior makes it useful in a variety of industrial and engineering applications such as drug manufacturing, paint and in armor construction. Blood, starch, nail polish and honey are such examples. The viscosity of these fluid changes with the rate at which the fluid shears...
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