GB2142290A - Wind tunnels - Google Patents

Abstract

For the circumstance when a wind tunnel model 7 in a ventilated tunnel generates such suction that air is drawn in via the ventilation, inevitably spoiling readings in a cone converging rapidly behind the model, this invention provides for suction on the ventilations from outside the working section together with a convergent working area. Slots 2 in the walls 1 open into plenum chambers 3 from which air may be drawn by pumps 5. The flexible walls 1 are adjustable by jacks 6. <IMAGE>

Description

SPECIFICATION Improvements in wind tunnels The present invention relates to wind tunnels.

It is particularly concerned with wind tunnels of the type having ventilated walls in the working section.

When ventilated wind tunnels are used to test models which generate suction right out to one or more of ventilated walls, air is drawn into the working section through the wall. The effects of this ingression can spread inwards quite rapidly downstream of the model and seriously affect the validity of any readings taken in the tunnel.

By the present invention means are provided in a ventilated wind tunnel for preventing ingression of fluid through the walls.

A ventilated working section wind tunnel according to the present invention has: a convergent working section, means for imposing a suction on the ventilated walls from outside the working section.

According to a feature of the invention the distribution of suction is arranged so as to minimise the interference flow camber and corrections to the gradient of free stream Mach number in use.

Advantageously the invention is realized in a wind tunnel wherein at least two opposing working section walls are flexible. Preferably the region behind the ventilations is compartmentalised so that different air pressure regimes can be established at different parts of ventilated walls. Insofar as this implies a plenum chamber or chambers behind the ventilated walls the outer wall to the plenum chamber or chambers may also be mobile.

A wind tunnel in accordance with the present invention will now be described by way of example with reference to the accompanying drawing, which is a schematic longitudinal section of a wind tunnel working area.

The drawing illustrates a wind tunnel working area having mobile ventilated side walls 1 in sections 1 a. The ventilation comprises slots 2 behind which there are plenum chambers 3 with associated air pumps 4 and gauges 5.

The sections 1 a are arranged for movement to a variety of stations by hydraulic jacks 6. The drawing also shows a model wing 7 in the tunnel working section.

In operation of the wind tunnel when a low pressure is to be generated by the model 7 which will extend to the walls 1, the sections 1 a are adjusted to a convergent configuration as shown and suction is applied to the plenum chambers 3 to give an approximation to a flow with minimum wall interference.

1. A ventilation working section wind tunnel having a convergent working section, and means for imposing a suction on the ventilated walls from outside the working section.

2. A wind tunnel as claimed in claim 1 and wherein the means for imposing a suction is adapted so to distribute suction as to minimise interference flow camber and correction to the gradient of free stream Mach number in use.

3. A wind tunnel as claimed in claim 1 or claim 2 and having opposing working section walls which are flexible.

4. A wind tunnel as claimed in any one of claims 1 to 3 and wherein the region behind the ventilations is compartmentalised so that different air pressure regimes can be established at different parts of ventilated walls.

5. A wind tunnel as claimed in any one of the preceding claims and having flexible plenum chamber outer walls.

6. A wind tunnel substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in wind tunnels The present invention relates to wind tunnels. It is particularly concerned with wind tunnels of the type having ventilated walls in the working section. When ventilated wind tunnels are used to test models which generate suction right out to one or more of ventilated walls, air is drawn into the working section through the wall. The effects of this ingression can spread inwards quite rapidly downstream of the model and seriously affect the validity of any readings taken in the tunnel. By the present invention means are provided in a ventilated wind tunnel for preventing ingression of fluid through the walls. A ventilated working section wind tunnel according to the present invention has: a convergent working section, means for imposing a suction on the ventilated walls from outside the working section. According to a feature of the invention the distribution of suction is arranged so as to minimise the interference flow camber and corrections to the gradient of free stream Mach number in use. Advantageously the invention is realized in a wind tunnel wherein at least two opposing working section walls are flexible. Preferably the region behind the ventilations is compartmentalised so that different air pressure regimes can be established at different parts of ventilated walls. Insofar as this implies a plenum chamber or chambers behind the ventilated walls the outer wall to the plenum chamber or chambers may also be mobile. A wind tunnel in accordance with the present invention will now be described by way of example with reference to the accompanying drawing, which is a schematic longitudinal section of a wind tunnel working area. The drawing illustrates a wind tunnel working area having mobile ventilated side walls 1 in sections 1 a. The ventilation comprises slots 2 behind which there are plenum chambers 3 with associated air pumps 4 and gauges 5. The sections 1 a are arranged for movement to a variety of stations by hydraulic jacks 6. The drawing also shows a model wing 7 in the tunnel working section. In operation of the wind tunnel when a low pressure is to be generated by the model 7 which will extend to the walls 1, the sections 1 a are adjusted to a convergent configuration as shown and suction is applied to the plenum chambers 3 to give an approximation to a flow with minimum wall interference. CLAIMS

1. A ventilation working section wind tunnel having a convergent working section, and means for imposing a suction on the ventilated walls from outside the working section.

2. A wind tunnel as claimed in claim 1 and wherein the means for imposing a suction is adapted so to distribute suction as to minimise interference flow camber and correction to the gradient of free stream Mach number in use.

3. A wind tunnel as claimed in claim 1 or claim 2 and having opposing working section walls which are flexible.

4. A wind tunnel as claimed in any one of claims 1 to 3 and wherein the region behind the ventilations is compartmentalised so that different air pressure regimes can be established at different parts of ventilated walls.

5. A wind tunnel as claimed in any one of the preceding claims and having flexible plenum chamber outer walls.

6. A wind tunnel substantially as hereinbefore described with reference to the accompanying drawing.