scholarly journals Improvement of the Full-Range Equation for Wave Boundary Layer Thickness

2020 ◽  
Vol 8 (8) ◽  
pp. 573 ◽  
Author(s):  
Hitoshi Tanaka ◽  
Nguyen Xuan Tinh ◽  
Ahmad Sana
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Full Range ◽  
Tsunami Waves ◽  
Wave Boundary Layer ◽  
Wide Range ◽  
Range Equation ◽  
Wave Boundary ◽  
Flow Experiments

In order to improve the accuracy of the original full-range equation for wave boundary layer thickness, with special reference to increasing its applicability to tsunami-scale waves, a theoretical investigation is carried out to derive a dimensionless expression which is valid under both smooth and rough turbulent regimes. A coefficient in the equation is determined through a comparison with k-ω  model computation results for tsunami-waves along with laboratory scale oscillatory flow experiments. Thus, the improved full-range equation for wave boundary layer thickness enables us to cover a wide range of wave periods from wind-wave to tsunami.

Influence of Chord Length and Inlet Boundary Layer on the Secondary Losses of Turbine Blades

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Helmut Sauer ◽  
Robin Schmidt ◽  
Konrad Vogeler
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Flow Direction ◽  
Velocity Ratio ◽  
Main Flow ◽  
Chord Length ◽  
Displacement Thickness ◽  
Wide Range ◽  
Main Flow Direction

In this paper, results concerning the influence of chord length and inlet boundary layer thickness on the endwall loss of a linear turbine cascade are discussed. The investigations were performed in a low speed cascade tunnel using the turbine profile T40. The turning of 90 deg and 70 deg, the velocity ratio in the cascade from 1.0 to 3.5 as well as the chord length of 100 mm, 200 mm, and 300 mm were specified. In a measurement distance of one chord behind the cascade in main flow direction, an approximate proportionality of endwall loss and chord was observed in a wide range of velocity ratios. At small measurement distances (e.g., s2/l=0.4), this proportionality does not exist. If a part of the flow path within the cascade is approximately incorporated, a proportionality to the chord at small measurement distances can be obtained, too. Then, the magnitude of the endwall loss mainly depends on the distance in main flow direction. At velocity ratios near 1.0, the influence of the chord decreases rapidly, while at a velocity ratio of 1.0, the endwall loss is independent of the chord. By varying the inlet boundary layer thickness, no correlation of displacement thickness and endwall loss was achieved. A calculation method according to the modified integral equation by van Driest delivers the wall shear stress. Its influence on the endwall loss was analyzed.

scholarly journals A scaling analysis for turbulent shock-wave/boundary-layer interactions

2013 ◽  
Vol 714 ◽  
pp. 505-535 ◽  
Author(s):  
L. J. Souverein ◽  
P. G. Bakker ◽  
P. Dupont
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Mass Conservation ◽  
Scaling Analysis ◽  
Pressure Jump ◽  
Interaction Length ◽  
Wave Boundary Layer ◽  
Wide Range ◽  
Mach Numbers ◽  
Wave Boundary

AbstractA model based on mass conservation properties is developed for shock-wave/boundary-layer interactions (SWBLIs), aimed at reconciling the observed great diversity in flow organization documented in the literature, induced by variations in interaction geometry and aerodynamic conditions. It is the basis for a scaling approach for the interaction length that is valid independent of the geometry of the flow (considering compression corners and incident-reflecting shock interactions). As part of the analysis, a scaling argument is proposed for the imposed pressure jump that depends principally on the free-stream Mach number and the flow deflection angle. Its interpretation as a separation criterion leads to a successful classification of the separation states for turbulent SWBLIs (attached, incipient or separated). In addition, the dependence of the interaction length on the Reynolds number and the Mach numbers is accounted for. A large compilation of available data provides support for the validity of the model. Some general properties on the state of the flow are derived, independent of the geometry of the flow and for a wide range of Mach numbers and Reynolds numbers.

Influence of Chord Length and Inlet Boundary Layer on the Secondary Losses of Turbine Blades

2010 ◽  
Author(s):  
Helmut Sauer ◽  
Robin Schmidt ◽  
Konrad Vogeler
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Flow Direction ◽  
Velocity Ratio ◽  
Turbine Blades ◽  
Flow Path ◽  
Chord Length ◽  
Displacement Thickness ◽  
Wide Range

In the present paper results concerning the influence of chord length and inlet boundary layer thickness on the endwall losses are discussed. The investigations were performed in a low speed cascade tunnel using the turbine profile T40. The deflection of 90 and 70 deg, the velocity ratio in the cascade from 1.0 to 3.5 as well as the chord length of 100,200 and 300 mm were predetermined. In a measurement distance behind the cascade of s2/l = 1, an approximate proportionality of endwall losses and chord length was observed in a wide range of velocity ratios. At small measurement distances (e.g. s2/l = 0.4), this proportionality does not exist. If aside from the flow path behind the cascade the flow path in the cascade is approximately incorporated, a proportionality to the chord length at small measurement distances can be obtained, too. Then to a large extent, the magnitude of the endwall losses is dependent on the length in main flow direction. At velocity ratios near 1.0, the influence of the chord length decreases rapidly, while at a velocity ratio of 1.0, the endwall losses are independent of chord length. By varying the inlet boundary layer thickness no correlation of displacement thickness and endwall losses was achieved. With a calculation method according to the modified integral equation by van Driest, the velocity gradient on the wall, the wall shear stress and the local friction coefficient were determined and their influence on the endwall losses analyzed.

Self-consistent unstirred layers in osmotically driven flows

2010 ◽  
Vol 662 ◽  
pp. 197-208 ◽  
Author(s):  
K. H. JENSEN ◽  
T. BOHR ◽  
H. BRUUS
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layers ◽  
Boundary Layer Thickness ◽  
Concentration Boundary ◽  
Concentration Boundary Layers ◽  
Unstirred Layers ◽  
Mathematical Relation ◽  
Wide Range ◽  
Self Consistent

It has long been recognized that the osmotic transport characteristics of membranes may be strongly influenced by the presence of unstirred concentration boundary layers adjacent to the membrane. Previous experimental as well as theoretical works have mainly focused on the case where the solutions on both sides of the membrane remain well mixed due to an external stirring mechanism. We investigate the effects of concentration boundary layers on the efficiency of osmotic pumping processes in the absence of external stirring, i.e. when all advection is provided by the osmosis itself. This case is relevant in the study of intracellular flows, e.g. in plants. For such systems, we show that no well-defined boundary-layer thickness exists and that the reduction in concentration can be estimated by a surprisingly simple mathematical relation across a wide range of geometries and Péclet numbers.

Modeling of controlled shock-wave/boundary-layer interactions in transonic channel flow

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 2293-2301
Author(s):  
R. Benay ◽  
P. Berthouze ◽  
R. Bur
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Channel Flow ◽  
Wave Boundary Layer ◽  
Wave Boundary

Insights in turbulence modeling for crossing-shock-wave/boundary-layer interactions

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 985-995 ◽  
Author(s):  
Frederic Thivet ◽  
Doyle D. Knight ◽  
Alexander A. Zheltovodov ◽  
Alexander I. Maksimov
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Turbulence Modeling ◽  
Wave Boundary Layer ◽  
Wave Boundary
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