Simplified Compressible Laminar Boundary- Layer Theory

1951 ◽  
Vol 18 (5) ◽  
pp. 358-359
Author(s):  
Arthur N. Tifford
Keyword(s):  
Boundary Layer ◽  
Laminar Boundary Layer ◽  
Boundary Layer Theory

scholarly journals Experimental observation of frequency lock-in of roughness-induced instabilities in a laminar boundary layer

2019 ◽  
Vol 870 ◽  
pp. 680-697
Author(s):  
Dominik K. Puckert ◽  
Ulrich Rist
Keyword(s):  
Boundary Layer ◽  
Aspect Ratio ◽  
Laminar Boundary Layer ◽  
Roughness Element ◽  
Water Channel ◽  
Three Dimensional ◽  
Boundary Layer Theory ◽  
Linear Stability Theory ◽  
Mode Decomposition ◽  
Lock In

The interaction of disturbance modes behind an isolated cylindrical roughness element in a laminar boundary layer is investigated by means of hot-film anemometry and particle image velocimetry in a low-turbulence laminar water channel. Both sinuous and varicose disturbance modes are found in the wake of a roughness with unit aspect ratio (diameter/height $=$ 1). Interestingly, the frequency of the varicose mode synchronizes with the first harmonic of the sinuous mode when the critical Reynolds number from three-dimensional global linear stability theory is exceeded. The coupled motion of sinuous and varicose modes is explained by frequency lock-in. This mechanism is of great importance in many aspects of nature, but has not yet received sufficient attention in the field of boundary-layer theory. A Fourier mode decomposition provides detailed analyses of sinuous and varicose modes. The observation is confirmed by a second experiment with the same aspect ratio at a different position in the laminar boundary layer. When the aspect ratio is increased, the flow is fully governed by the varicose mode. Thus, no frequency lock-in can be observed in this case. The significance of this work is to explain how sinuous and varicose modes can co-exist behind a roughness and to propose a mechanism which is well established in physics but not encountered often in boundary-layer theory.

An Analysis of the Flow of Oil Through a Tapered Roller Bearing

1972 ◽  
Vol 94 (2) ◽  
pp. 125-130 ◽  
Author(s):  
R. L. Leibensperger
Keyword(s):  
Boundary Layer ◽  
Theoretical Analysis ◽  
Laminar Boundary Layer ◽  
Roller Bearing ◽  
Boundary Layer Theory ◽  
Tapered Roller Bearing ◽  
Outer Race ◽  
Tapered Roller ◽  
Viscous Torque

A theoretical analysis, based on boundary layer theory, is presented to predict the oil pumping ability of a tapered roller bearing. The momentum integrals for an assumed laminar boundary layer about the I.D. circumference of the outer race (cup) are derived and solved numerically. The resulting equations predict that the head, flow and viscous torque generated are dependent upon the bearing’s speed and geometry, as well as the viscosity and density of the oil in the bearing.

Study of the Cooling Wall Boundary Layer with Underfloor Supply Room

2011 ◽  
Vol 287-290 ◽  
pp. 2575-2578
Author(s):  
Xiao Hua Li ◽  
Dao Guang Lin
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Laminar Boundary Layer ◽  
Air Temperature ◽  
Boundary Layer Theory ◽  
Calculation Formula ◽  
Theory Analysis ◽  
Temperature Calculation ◽  
Wall Boundary Layer ◽  
Main Region

Based on the underground supply room properties and the boundary layer theory, this paper derived the temperature calculation formula of the laminar boundary layer and turbulent boundary layer, respectively; then discussed the mass flow calculation formula of the boundary layer; at the end experiment indicated the boundary layer definitely exits between the main region and the outside structure, whose temperature is between the air temperature of the main region and the air temperature of the wall. It validated that the theory analysis is correct.

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