Studies on Boundary Layer Blockage and Choking in High-Velocity Transient Motors

2006 ◽  
Author(s):  
Vr Sanalkumar ◽  
Bn Raghunandan ◽  
T Kawakami ◽  
Hd Kim ◽  
T Setoguchi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Velocity

Effect of boundary-layer removal on high velocity flame stabilization

AIAA Journal ◽  
1964 ◽  
Vol 2 (11) ◽  
pp. 2030-2031
Author(s):  
JAMES R. MAUS ◽  
WILLIAM T. SNYDER
Keyword(s):  
Boundary Layer ◽  
High Velocity ◽  
Flame Stabilization ◽  
Layer Removal

A New Method to Measure Prandtl Number and Thermal Conductivity of Fluids

1957 ◽  
Vol 24 (1) ◽  
pp. 25-28
Author(s):  
E. R. G. Eckert ◽  
T. F. Irvine
Keyword(s):  
Thermal Conductivity ◽  
Boundary Layer ◽  
Prandtl Number ◽  
High Velocity ◽  
Atmospheric Pressure ◽  
New Method ◽  
Test Results ◽  
Test Setup ◽  
Velocity Boundary Layer ◽  
Layer Flow

Abstract A new method is described by which the Prandtl number and indirectly the thermal conductivity of fluids can be measured. The method is based on the fact that a well-established, unique relation exists between the Prandtl number and the recovery factor for laminar high-velocity boundary-layer flow. The test setup is described which has been devised for such measurements, and test results are presented for air at atmospheric pressure and temperatures between 60 and 350 F.

Step-induced turbulence in a high-velocity boundary layer

1989 ◽  
Vol 24 (1) ◽  
pp. 150-153
Author(s):  
V. Ya. Kiselev ◽  
V. I. Lysenko
Keyword(s):  
Boundary Layer ◽  
High Velocity ◽  
Velocity Boundary Layer

The Hydrodynamical Performance of Migratory Salmon

1961 ◽  
Vol 38 (2) ◽  
pp. 365-390
Author(s):  
M. F. M. OSBORNE
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Fuel Consumption ◽  
High Velocity ◽  
Columbia River ◽  
Water Velocity ◽  
Superior Performance ◽  
General Effect ◽  
Flood Peak ◽  
Velocity Water

The annual spawning migration of Pacific Coast salmon up the Columbia and Amur rivers has been analysed as an experiment on the maximum range of an unefuelled vehicle, since the fish do not eat during this migration. The fuel (primarily fat) available to real fish is compared to that computed for an equivalent rigid vehicle with the following performance specifications which may be regarded as optimum ones for marine vehicles. 1. A choice for the speed of ascent against the average river current corresponding to the least fuel consumption, without seeking systematically either low- or highvelocity water. 2. A drag coefficient corresponding to a turbulent boundary layer with no separation. 3. An overall efficiency of 24% for converting the heat of combustion of the fuel to directed kinetic energy in the wake. Under these assumptions, the vehicles usually require slightly more fuel than the corresponding fish which they are intended to approximate; in the case of blueback salmon, the vehicle requires about five times as much. One, therefore, concludes that the fish have a performance superior to that of the best engineered rigid vehicles, as defined and operated under the above three specifications. Suggested explanations for the apparently superior performance of the fish are: (1) a deliberate seeking, by the fish, of low-velocity water close to the bottom or shoreline; (2) the ability of the fish to maintain a laminar rather than turbulent boundary layer; (3) the ability of the fish to extract energy from the turbulent velocity fluctuationsof the river. Analysis of salmon counts over the Bonneville and Rock Island dams on the Columbia River shows that the average velocity of the fish upstream is influenced by the velocity of the water downstream in the following peculiar fashion, depending upon whether one considers water-velocity variations through the course of a year, or variations at a fixed season of the year, from one year to the next. The general effect of the water velocity as it varies through a year, is to slow the fish down when the water velocity is large (at the June flood peak) and to permit faster ascent when the water velocity is less, in both preceding and following months. But at a fixed season of the year, prior to the flood peak in June, relatively high-velocity water speeds the fish up. At a fixed season after the flood peak, relatively high-velocity water slows them down. These relationships are in agreement with other biological observations and with an analysis of navigation for minimum fuel consumption. Data and methods are given permitting a calculation of the average water velocity in the Columbia River, from the mouth to the headwaters, for any season of the year.

Turbulent Film Condensation on a Horizontal Elliptical Tube

2003 ◽  
Vol 125 (6) ◽  
pp. 1194-1197 ◽  
Author(s):  
Cha’o-Kuang Chen ◽  
Hai-Ping Hu
Keyword(s):  
Boundary Layer ◽  
High Velocity ◽  
Potential Flow ◽  
Tangential Velocity ◽  
Flow Theory ◽  
Interfacial Shear ◽  
Experimental Results ◽  
Film Condensation ◽  
Vapor Flow ◽  
Tube Surface

This is an investigation of turbulent film condensation on a horizontal elliptical tube. The high tangential velocity of the vapor flow at the boundary layer is determined from potential flow theory. The Colburn analogy is used to define the local liquid-vapor interfacial shear which occurs for high velocity vapor flow across an elliptical tube surface. The results developed in this study are compared with those generated by previous theoretical and experimental results.

Controlling Aerodynamic Characteristics of High-Velocity Airfoils by External Energy Supply

2010 ◽  
Vol 5 (3) ◽  
pp. 47-512
Author(s):  
Sergey M. Aulchenko ◽  
Vladimir P. Zamuraev ◽  
Anna P. Kalinina
Keyword(s):  
Boundary Layer ◽  
High Velocity ◽  
Energy Supply ◽  
Aerodynamic Characteristics ◽  
External Energy ◽  
Gas Density ◽  
Boundary Layer Approximation

The influence of pulsed-periodic (proportional to gas density) energy supply on the aerodynamic characteristics of high-velocity airfoils was studied. The value of the period of the energy supply was varied. The influence of viscosity in the boundary layer approximation has been taken into consideration as well

High-velocity flow in a rough fracture

1999 ◽  
Vol 383 ◽  
pp. 1-28 ◽  
Author(s):  
E. SKJETNE ◽  
A. HANSEN ◽  
J. S. GUDMUNDSSON
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Flow Field ◽  
High Velocity ◽  
Average Velocity ◽  
Flow Tube ◽  
Low Velocity ◽  
Viscous Term ◽  
High Velocity Flow ◽  
Velocity Flow

We simulate high-velocity flow in a self-affine channel with a constant perpendicular opening by solving numerically the Navier–Stokes equations, and analyse the resulting flow qualitatively and quantitatively. At low velocity, i.e. vanishing inertia, the effective permeability is dominated by the narrowest constrictions measured perpendicular to the local flow direction and the flow field tends to fill the channel due to the diffusion generated by the viscous term in the Stokes equation. At high velocity (strong inertia), the high-velocity zones of the flow field resemble a narrow tube of essentially constant thickness in the direction of flow, since the transversal diffusion is weak compared to the longitudinal convection. The thickness of the flow tube decreases with Reynolds number. This narrowing in combination with mass balance results in an average velocity in the flow tube which increases faster with Reynolds number than the average velocity in the fracture. In the low-velocity zones, recirculation zones appear and the pressure is almost constant.The flow tube consists of straight sections. This is due to inertia. The local curvature of the main stream reflects the flow-tube/channel-wall interaction. A boundary layer is formed where the curvature is large. This boundary layer is highly dissipative and governs the large pressure loss (inertial resistance) of the medium. Quantitatively, vanishing, weak and strong inertial flow regimes can be described by the Darcy, weak inertia and Forchheimer flow equations, respectively. We observe a cross-over flow regime from the weak to strong inertia, which extends over a relatively large range of Reynolds numbers.

Steady flow in rapidly rotating variable-area rectangular ducts

1975 ◽  
Vol 69 (2) ◽  
pp. 209-227 ◽  
Author(s):  
John S. Walker
Keyword(s):  
Boundary Layer ◽  
High Velocity ◽  
Flow Direction ◽  
Side Wall ◽  
Vertical Axis ◽  
Present Theory ◽  
Centrifugal Pumps ◽  
Good Test ◽  
Axis Of Rotation ◽  
Constant Area

Steady liquid flow in a variable-area rectangular duct rotating rapidly about an axis perpendicular to its centre-line is treated. This problem is significant because the idea of driving a liquid through a rotating system has been largely overlooked by rotating-fluid dynamicists and because it closely resembles the flow inside the impellers of centrifugal pumps and hydraulic turbines. For a prototype formed by joining a semi-infinite constant-area duct and a semi-infinite duct with straight diverging walls, the flow in the diverging duct is carried entirely by large, O(E1/3) velocities in a boundary layer of thickness O(E1/3) adjacent to one of the (side) walls parallel to the axis of rotation, where E is the (small) Ekman number. With a vertical axis of rotation this high-velocity boundary layer is adjacent to the side wall on the right when facing in the flow direction. For a diverging or converging duct placed between two semi-infinite constant-area ducts, large, O(E1/3) velocities occur in side-wall boundary layers on both sides of the variable-area duct and on the left and right sides of the upstream and downstream constant-area ducts respectively. The existence of high-velocity side layers in rapidly rotating rectangular ducts should be relatively easy to prove experimentally and actual measurements of their velocity profiles would provide a good test of the present theory.

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