GB2301188A - Apparatus and method for determining wind direction or other flow direction - Google Patents

Abstract

A static wind-direction indicator comprises a plurality of "hot wire" anemometer sensors A, each having an associated shield B disposed to one side thereof, the location of each shield B with respect to its associated sensor A being different, so that for a given wind strength the relative values of the signals from the respective sensors A are different for different wind directions. Processing means (30, Fig. 4) connected with all of the sensors can therefore deduce the wind direction from the sensor signals, to provide a direction indication on a display (46). The processing means may also be arranged to deduce from the signals from the sensors, and to indicate, the wind speed; air temperature may also be measured. Other applications, e.g. to ocean current measurements, are envisaged.

Description

DESCRIPTION OF INVENTION Title: "Apparatus and method for determining wind direction or other flow direction" THIS INVENTION relates primarily to the determination of wind direction but may also be applicable to the determination of flow direction in anaiogous situations such as air flow in buildings, ocean currents and so on.

It is normal practice to determine the direction from which an air stream or wind blows by means of a freely rotatable vane which aligns itself to the direction of flow. The wind direction is then determined either visually or by using electro-mechanical, electro optic or electro magnetic sensors which supply information relating to the vane position to the instrument.

It is among the objects of the invention to provide apparatus for determining wind or other fluid flow direction which does not rely on moving parts.

According to the invention there is provided apparatus for determining wind or other fluid flow direction comprising a group of sensor devices producing signals dependent on wind speed or other fluid flow speed past said devices and a fluid flow modifying structure or structures associated with said group of sensor devices such that for a given wind speed or other fluid flow speed, the relative magnitudes of the signals from said devices vary with wind direction and processing means receiving said signals from all of said devices and arranged to provide an indication of wind or other fluid flow direction.

Preferably the sensor devices are devices operating on the "hot wire" principle, for example electrically resistive wires heated by passing electric current through them, with the instantaneous resistance or associated quantity such as current or voltage providing an indication of cooling by airflow over the wires or analogous devices such as thermistors used in the same way.

Embodiments of the invention are described below by way of example with reference to the accompanying drawings, in which: FIGURES l(a) and l(b) are perspective views illustrating structures illustrating the principle of the invention; FIGURES 2(a), 2(b) and 2(c) are diagrammatic plan views illustrating the structure of Figure l(a) placed in an air flow from respective different directions, FIGURE 3(a) is a perspective view and FIGURE 3(b) a plan view illustrating a group of sensors and flow modifying structures in accordance with the invention, and FIGURE 4 is a schematic block diagram of the whole apparatus.

Referring to Figure 1(a), this shows a thermistor A supported, by its leads extending in opposite directions, between a supporting base 10 and a pylon 12 so that the thermistor A is spaced from the base 10 and exposed to air flow on all sides. The thermistor is supplied with electrical current by circuitry, not shown but known per se, which is sensitive to the voltage across the thermistor. The electrical current heats the thermistor A from which heat is lost to the surrounding air. The more rapid the air flow past the thermistor, the greater the cooling effect.The circuitry connected with the thermistor A can, in effect, determine its temperature from the electrical resistance and can, in effect, determine the energy supplied to the thermistor (and lost as heat) from the voltage applied and the current passed through the thermistor and can on this basis, derive a signal corresponding to the speed of air flow past the thermistor A. That is to say, the thermistor acts as an air speed sensor operating on the "hot wire" principle. The thermistor A may, indeed, be replaced by an electrically resistive fine metal wire - a thermistor is preferred simply because of its greater temperature sensitivity and physical robustness.For simplicity, in the following, the air flow sensors will be referred to as thermistors, but it will be appreciated that they can be electrically resistive wires, or can be semiconductor devices of various types exhibiting adequate sensitivity to temperature. Whilst such a "hot-wire" sensor is capable, as is well known, of measuring wind speeds with high accuracy, it is not inherently capable of determining wind direction.

Referring again to Figure 1, a shield B is mounted on the base 10, spaced from the thermistor A. The shield B is shown as being in the form of a concave partcylindrical plate with its concave side facing the thermistor A, and with its axis of curvature perpendicular to base 10 and passing through the thermistor A, but, as will appear from the following, the precise configuration is relatively unimportant. An alternative construction, using a flat shield B, is shown in Figure l(b) by way of example.

Referring to Figure 2(a), if the structure shown in Figure l(a) is placed in an air stream so that the shield B is immediately upstream of the thermistor A, the thermistor A will be sheltered from the air stream so that the cooling effect upon the thermistor will be substantially less than if the shield B were not present.

On the other hand, if the assembly is disposed relative to the air-stream, as shown in Figure 2(b), so that, relative to the overall flow direction of the airstream the shield B is disposed to one side of the thermistor, so that the cooling effect upon the thermistor will be little different from the effect if the shield were absent. There should clearly be no difference on the cooling effect if the air flow direction were simply reversed in Figure 2(b). If the air flow direction were reversed in Figure 2(a) (as shown in Figure 2(c)), one might expect the cooling effect to be slightly reduced as compared with Figure 2(b) but to a substantially lesser degree than in Figure 2(a).Thus, the structure of Figure l(a) and likewise that of Figure l(b) is sensitive to wind direction but is still unable to provide an unambiguous indication of wind direction.

However, if a plurality of such structures is provided, arranged in a group in which the orientation of each thermistor/shield combination is different from that of the others, it becomes possible to arrive at an unambiguous determination of wind direction, for in this case reversals of flow direction which would leave some of the sensors substantially unaffected would have a significant effect on differently oriented sensors.

Furthermore, the arrangement shown in Figures 3(a) and 3(b) is, unlike that of Figures l(a) or l(b) capable of distinguishing the effect of a change in wind direction from the effect of wind speed, since, for example, the cooling rate of the most effectively cooled thermistor A in Figures 3(a) and (b) for a given wind direction, will be greater the greater the wind speed.

In the arrangement of Figures 3(a) and (b), each thermistor may have associated therewith a respective conventional circuit to provide an indication of the actual airflow over the respective thermistor. The outputs of these circuits may, in turn, be passed to processing circuitry arranged to derive, from these signals, the desired indication of wind direction. Alternatively, the processing circuitry may simply be provided with "raw" signals from the thermistors A, for example voltage signals from the thermistors A (each supplied with a constant current), or the thermistor A may have respective circuits performing some intermediate level of processing before supplying respective signals to the processing circuitry.

In the arrangement shown, in Figure 4, the signals from the individual thermistors or hot wires or from the individual circuits, indicated at 20, associated therewith, are passed to a neural network 30 providing an output, significant of wind direction, to an instrument 40 which may, for example, drive a display 46 and/or record the wind direction and/or transmit data relating to the wind direction to a remote location.

The group of similar elements (thermistor/shield combination) dispersed in different directions will give a different pattern for each direction. A form of artificial intelligence within the neural network could be programmed to learn the "finger prints" of cooling effect on the various thermistors/hot wires for different wind directions and speeds. The neural network may be replaced by a conventional computer with respective ports for signals from each of the thermistors. The conventional digital computer may be programmed to simulate a neural network, or may be more conventionally programmed.

The same thermistors could be used to measure the ambient temperature by reducing the self heating current to prevent self heating. Wind velocity can be measured by calibrating each thermistor and monitoring the thermistor with highest self heating. Alternatively, of course, a separate thermistor or "hot wire" could be provided for measuring wind speed in any direction. Likewise, a separate thermistor or other temperature sensor may be provided for measuring air temperature regardless of wind speed or direction.

The configuration of thermistor/hot wire and shield combinations can be constructed in may different ways, i.e.

say, horizontally mounted, vertically mounted, spirally spaced etc.

Furthermore, each thermistor/hot wire and shield combination may be constructed differently from the arrangements illustrated in Figures l(a) and 1(b). In particular, each pylon 12 may be replaced by a supporting member extending from, or forming part of the respective shield B.

Whilst, with the arrangement illustrated in Figures 3(a) and 3(b) the individual thermistor/shield combinations may be spaced so far from each other that no such combination has any significant effect on the air flow over the others, the thermistor/shield combination may be so closely arranged that each does affect the air flow over the others. In the latter case, indeed, it may not be necessary for each thermistor to have a separate shield.

For example, at one extreme, a single shield may be surrounded by a ring of thermistors, or, in intermediate cases, a group of shields, or a relatively complex shielding structure may be arranged relative to a group of thermistors so as to afford an arrangement particularly sensitive to wind direction.

In summary, the invention makes it possible to provide a solid state wind direction measuring instrument with no moving parts and which can be miniaturised into a small package for measuring wind speed/wind temperature and wind direction.

Claims (11)

1. Apparatus for determining wind or other fluid flow direction comprising a group of sensor devices producing signals dependent on wind speed or other fluid flow speed past said devices and a fluid flow modifying structure or structures associated with said group of sensor devices such that for a given wind speed or other fluid flow speed, the relative magnitudes of the signals from said devices vary with wind direction and processing means receiving said signals from all of said devices and arranged to provide an indication of wind or other fluid flow direction,

2. Apparatus according to claim 1 wherein said sensor devices are devices operating on the "hot wire" principle.

3. Apparatus according to claim 1 or claim 2 wherein said fluid flow modifying structure comprises, for each of at least some of said sensor devices, a respective shield disposed to one side of the respective said device.

4. Apparatus according to any preceding claim wherein said processing means comprises a neural network.

5. Apparatus according to any of claims 1 to 4 wherein said processing means comprises a digital computer arranged to simulate a neural network.

6. Apparatus according to any preceding claim wherein said processing means is additionally arranged to provide an indication of wind speed or other fluid flow speed.

Apparatus according to claim 2 which is also operable to measure air temperature.

8. A method of determining wind or other fluid flow direction, comprising providing apparatus according to claim 1, placing said group of sensor devices and associated flow modifying structure or structures in the air or other fluid flow to be sensed, and operating said processing means to determine wind or other flow direction.

9. Apparatus for measuring wind direction, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

10. A method of determining wind or other fluid flow direction, substantially as hereinbefore described with reference to the accompanying drawings.

11. Any novel feature or combination of features described herein.