Calculation of tunnel wall interference from wall-pressure measurements

1988 ◽  
Vol 92 (911) ◽  
pp. 36-53 ◽  
Author(s):  
P. R. Ashill ◽  
R. F. A. Keating
Keyword(s):  
Experimental Evaluation ◽  
Solid Wall ◽  
Wall Pressure ◽  
Wind Tunnels ◽  
Pressure Measurements ◽  
Complex Flows ◽  
Tunnel Wall ◽  
Model Flow ◽  
Good Agreement

Summary A method is described for calculating wall interference in solid-wall wind tunnels from measurements of static pressures at the walls. Since it does not require a simulation of the model flow, the technique is particularly suited to determining wall interference for complex flows such as those over VSTOL aircraft, helicopters and bluff shapes (e.g. cars and trucks). An experimental evaluation shows that the method gives wall-induced velocities which are in good agreement with those of existing methods in cases where these techniques are valid, and illustrates its effectiveness for inclined jets which are not readily modelled.

Numerical and experimental investigations on the reduction of wind tunnel wall interference by means of adaptive slots

2001 ◽  
Vol 105 (1052) ◽  
pp. 571-580 ◽  
Author(s):  
O. Meyer ◽  
W. Nitsche ◽  
I. Futterer
Keyword(s):  
Wind Tunnel ◽  
Test Section ◽  
Wind Tunnels ◽  
Experimental Investigations ◽  
Reference Case ◽  
Tunnel Wall ◽  
Promising Alternative ◽  
Model Flow ◽  
Flexible Walls ◽  
Basic Studies

Abstract The flow in many wind tunnel experiments is affected by the presence of test section walls. The resulting interference can be minimised by correcting the measured model pressures, or by influencing the model flow directly with the use of ventilated or adaptive test section walls. The objective behind the latter technique is to guide the flow in the test section to achieve low interference (i.e. free flow) condition at the model. The most successful technique of flexible, adaptive walls is still restricted to small research wind tunnels due to its mechanical complexity. However, a very promising alternative is the use of adaptive slots in the test section walls. This concept combines the method of passive slotted walls, as they are already implemented in many large wind tunnels, and flexible walls. Additionally, this technique presents the opportunity of full 3D adaptations because the slots can be situated in all four test section walls. This paper presents preliminary experimental results and the latest numerical calculations on the effectiveness of adaptive slots. The experiments were conducted under high subsonic flow conditions in the new slotted test section of the transonic wind tunnel at TU Berlin’s Aeronautical Institute (ILR). The numerical results presented are focussed on the 2D slot adaptation of a 2D-model (CAST7 aerofoil) and the 3D slot adaptation of a body of revolution (3D-ETB). In addition, basic studies were made of the flows associated with a single slot on one wall and a bump on the other. The numerical and the first experimental investigations have shown the potential of adaptive slots to reduce wall interferences effectively. The adaptation accuracy of the investigated slot configurations deviated not more than 3% from the reference case (2D-wall adaptation).

Pressure Measurements on Flapped Hydrofoils in Cavity Flows and Wake Flows

1967 ◽  
Vol 11 (03) ◽  
pp. 170-189
Author(s):  
M. C. Meijer
Keyword(s):  
Wall Effect ◽  
Cavity Flows ◽  
Pressure Measurements ◽  
Viscous Effect ◽  
Tunnel Wall ◽  
Experimental Procedure ◽  
Wake Flows ◽  
Theoretical Predictions ◽  
Theory And Experiments ◽  
Good Agreement

The purpose of the present experiments is to obtain detailed information about the flow field, such as the pressure distribution, at the surface of a flapped hydrofoil in full cavity or wake flows. The model and the experimental procedure are described. The experimental results obtained have been used to compare with the theoretical predictions, to investigate the tunnel wall effect and to estimate the viscous effect at a sharp corner. Anempirical method for correcting the tunnel wall effect is developed here, the validity of which is supported by tests with models of three different sizes. An appreciable Viscous effect has been found near the hinge of a deflected flap. Except for this effect, the theory and experiments are found to be in good agreement.

Development of a new class of precast concrete pipes - an experimental evaluation

2007 ◽  
Vol 34 (7) ◽  
pp. 885-889 ◽  
Author(s):  
H El Naggar ◽  
E N Allouche ◽  
M H. El Naggar
Keyword(s):  
Experimental Evaluation ◽  
Solid Wall ◽  
Research Effort ◽  
Precast Concrete ◽  
Load Test ◽  
Added Value ◽  
Structural Performance ◽  
Concrete Pipes ◽  
Concrete Pipe ◽  
Cellular Concrete

Concrete pipes represent the backbone of the municipal storm and wastewater collection systems of Ontario, Canada. Industry and academia partnered on a research effort that aimed at developing new precast-concrete pipe products that provide added value to the final user in comparison with existing products. This paper describes a full-scale experimental evaluation of the design, manufacturing, and performance aspects of a "cellular" concrete pipe, a precast concrete pipe in which multiple continuous conduits were incorporated within its wall. Two fully-instrumented prototype segments of the proposed cellular concrete pipe were manufactured using standard dry-cast manufacturing procedures. The pipe segments were subjected to a D-load test to evaluate their structural performance. The observed structural performance was found to be comparable to solid-wall specimens, particularly when a four-conduit configuration was used. Of the six materials used as conduits, PVC and aluminum were found to perform the best. The presence of the conduits appears to delay the on-set of major cracks, thus increasing the D-load value. Key words: precast, concrete, pipe, experimental, conduit system, trenchless construction methods.

A Shock-Tube Technique to Determine Steady-Flow Losses of Orifices and Other Duct Elements

1960 ◽  
Vol 82 (1) ◽  
pp. 195-200 ◽  
Author(s):  
George Rudinger
Keyword(s):  
Shock Tube ◽  
Steady Flow ◽  
Discharge Coefficient ◽  
Initial Conditions ◽  
Test Element ◽  
Pressure Measurements ◽  
Flow Data ◽  
Flow Rates ◽  
Flow Losses ◽  
Good Agreement

It is shown that a simple shock tube is capable of producing appreciable steady-flow rates through a short duct element, such as an orifice, a valve, or a screen. The flow upstream and downstream of the test element and, therefore, also the losses caused by the test element, can be calculated from known initial conditions in the shock tube and pressure measurements at one point upstream of the element. Experiments to determine the discharge coefficient of a sharp-edged orifice are described as an illustration of the method. The results are in good agreement with available steady-flow data.

Unsteady Wall Pressure Measurements In An Outflow Butterfly Valve Using Remote Microphone Probes

2016 ◽  
Author(s):  
Aurelien Marsan ◽  
Marlene Sanjose ◽  
Yann Pasco ◽  
Stephane Moreau ◽  
Martin Brouillette
Keyword(s):  
Wall Pressure ◽  
Pressure Measurements ◽  
Butterfly Valve

On the theory of two-dimensional wind tunnels with porous walls

1955 ◽  
Vol 233 (1192) ◽  
pp. 74-90 ◽  
Keyword(s):  
Mach Number ◽  
Pressure Gradient ◽  
Solid Wall ◽  
Porous Wall ◽  
Effective Length ◽  
Wind Tunnels ◽  
Special Cases ◽  
Porous Surfaces ◽  
Independent Variable ◽  
Porous Walls

A mathematical theory is developed enabling wind tunnels with porous walls to be designed to give zero tunnel blockage in subsonic compressible flow. The tunnel walls are taken to be porous over only a finite range R , and solid elsewhere, and a sealed jacket is placed over the porous section so that the pressure on the outside of the porous wall can be controlled. The porous wall is assumed to have the characteristic that the component of velocity normal to it is proportional to the pressure drop across it, the constant of proportionality, λ, being termed the ‘porosity’ of the wail. Infinite porosity and zero porosity correspond to free streamline and solid wall boundaries respectively, which are thus included in the theory as special cases. The problem solved in this paper is to determine the relation between λ, R , the tunnel height H , and the Mach number M , so that the ‘blockage’, or velocity increment at the model caused by the tunnel walls, vanishes. It is found that for a given value of the porosity the length of the porous wall, R , must be reduced with increasing Mach number to keep the blockage zero. Thus the tunnel needs to be fitted with adjustable sections of solid wall which can be moved across the porous surfaces to reduce their effective length (see figure 1). Both ‘solid ’ and ‘wake’ blockage are considered in the paper. The effects of wake blockage, which are particularly important at high subsonic speeds due to the rapid increase in drag, cannot be completely eliminated by varying R alone. This is because wake blockage, unlike solid blockage, causes a pressure gradient in the tunnel. This gradient and the blockage can be eliminated simultaneously only by introducing a further independent variable. A very convenient one for this purpose can be created by pumping air at a certain rate from the jacket and exhausting it outside the tunnel. The rate of removal of the air from the jacket can be adjusted to eliminate the induced pressure gradient completely.

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