Even his son Miryu does not know that his father is the legendary devil. Daily Duo Liza.
Vintage s 3.
By making each successive power injection larger than the one before, one can build up almost any degree of gain, or amplification, one wishes.
That is to say, the small nudge, or signal, applied by a control jet in the first stage can be amplified by successive steps to control a very large power stream indeed in the final stage. This, then, is the basic outline of the first of the two fluid-control techniques under study.
As an instrument of proportional control it performs amplification in the usual sense of the word, and it promises a number of interesting applications, including its use as an element in an analogue computer.
The other technique of fluid control does not produce proportional amplification; rather, it corresponds to a triode that turns a flow of electrons on or off. It is essentially like an element in a digital computer. In this system the fluid power stream, left to itself, locks onto one wall of the channel in which it is flowing, and as a result the stream exits through the outlet on that side.
An injection of fluid from the control jet on the same side will cause the stream to swing over to the other side and lock onto the wall there, so that it then flows out of the other outlet. In either case the stream maintains a stable position, flowing only to a particular outlet unless it is switched by a control jet.
The reasons for this are inherent in the mechanics of the situation. Consider a high-speed stream of air injected through a nozzle into a wide container of air. I call the fluid air to make the example specific; the results to be described would apply to any gas or liquid.
The stream's pickup of air along its sides, however, causes the pressure to drop in the zones between the stream and the walls of the container. The resulting pressure difference creates an unstable situation: the higher pressure of the surroundings "ambient pressure" will push air back into the low-pressure zones on both sides of the stream to equalize the pressure.
Suppose now there is some disturbance or asymmetry say in the shape of the container that causes the equalizing return flow to push the stream toward one wall. As the zone between the stream and that wall narrows, there is less room for the admittance of counterflow to replace the air being entrained by the stream on that side and therefore the comparative pressure in the zone drops further.
Very quickly the stream moves over against the wall. It stays locked onto that wall as long as the stream keeps flowing, because on the wall side a region of low pressure persists near the nozzle, whereas on the opposite side of the stream the ambient pressure pushes the stream toward that region.
The phenomenon is known as the Coanda effect -- so designated because it was first studied by a Romanian engineer named Henri Coanda in the 's. This can easily be done by means of control jets on the sides. If the stream is locked onto the right wall, injection of air from the right jet or removal of air through the left jet will cause the stream to swing away from the right wall as soon as the pressure on the right side becomes higher than that on the left.
Once the stream has crossed the center line of the channel it will go on to attach itself to the left wall for the same reasons that it originally locked onto the right one.
The control jet can then be shut off, the stream will stay locked onto the left side without help. In the two-outlet type of device the locking of the stream onto the right wall means, of course, that the entire stream exits through the right outlet, and when it is switched to the left wall, it goes to the left outlet.
The Coanda effect explains, by the way, why the proportional-contro1 amplifier must have the channel widened into a heart shape near the power-stream nozzle; this configuration prevents the stream from locking onto a wall.
It has turned out that the behavior of the stream depends a great deal on the distance of the splitter from the power-stream nozzle. When the splitter is very close to the nozzle within a distance not more than about twice the nozzle's width , the stream does not lock onto either wall, because the distance is not sufficient for a significant pressure difference to develop.
The stream can be directed into one outlet or the other by a pulse injection from a control jet, but as soon as the control injection stops, the stream resumes its normal behavior of dividing at the splitter and flowing to both outlets. If the splitter is located at a distance amounting to three to five nozzle widths from the nozzle, the stream begins to be influenced by the Coanda effect: in the presence of an asymmetry most of it will flow spontaneously to one outlet.
When the splitter is six nozzle widths or more away from the nozzle, the Coanda effect takes full charge. The stream will lock onto one wall and flow only to the outlet it has chosen spontaneously or the one to which it is switched. Some very interesting effects can be produced by blocking one of the outlets, as the illustration on page 85 shows.
In one arrangement such a block will divert the stream from the outlet it naturally prefers to the opposite one, but when the block is removed the stream will return spontaneously to the preferred outlet! Thus the device exhibits a property that amounts to memory, and it can be put to use for that purpose.
Of the various possible uses of fluid control devices the most intriguing is their application as the basis of a digital computer. The type of device in which the stream locks onto one wall or the other is precisely suited for functioning as an all-around element for such a computer. It gives a binary digital response: the stream can be directed to either of two exit ports, one representing 0, the other representing 1.
It can be shifted back and forth from one port to another like a flip-flop switch. Indeed, it can even serve as an oscillator. This can be accomplished by connecting the control jets on the opposite sides of the main stream by a tube that will transmit sound.
VV hen the main stream flops from one side to the other, it generates sound waves -- a compression wave on one side of the stream and a rarefaction wave on the other. If the sonic path through the tube connecting the two sides has a length that is about half the wavelength of the full sound wave, the compression and rarefaction waves, traveling through the tube in opposite directions, will cross to the opposite sides in the same time.
This change in pressure at the respective sides from compression to rarefaction on one side and from rarefaction to compression on the other is sufficient to switch the main stream from one wall to the other. The stream will oscillate back and forth as the sound waves travel back and forth.
The fluid device can also be designed to act as a logical gate expressing the concept "and" or "or. The fluid-control concept lends itself to a great variety of arrangements.
The device can be designed, for example,. By building a network of channels of varying cross section and with varying conntrols it is possible to create a system that will carry out a series of different operations. And the characteristics of the system can be varied by using various fluids.
In most of the computational elements constructed so far the working fluid is air, because it is so readily available and easy to handle. Let us look now at a couple of specific applications of fluid control on which considerable research has been done.
One is the steering of rockets in flight.
This is managed at present by the use of devices such as jet vanes and swiveled nozzles through which pulses of exhaust are discharged to apply small thrusts correcting the trajectory of the rocket. These devices are far from ideal, because it takes a great deal of force to operate them, their response to commands is fairly slow andf they involve moving parts that are subject to being put out of action by the hot exhaust streams.
A fluid-control system now under study would avoid those difficulties. The control would be applied to the main exhaust stream itself, that is, the thrust that drives the rocket. The small stream would be controlled by a pair of jets; when the right jet was turned on, it would turn the stream so that it struck the main exhaust from the side, thereby changing the direction of the driving thrust slightly with a resulting change in the trajectory of the rocket's flight.
The idea has been tested in a small land vehicle powered by a turbine engine. By means of a five-stage proportional amplifier weighing less than 10 pounds, an extremely small fluid signal amounting to a flow of less than five thousandths of a pound per minute controlled a jet of 33 pounds per minute that was used to deflect the power stream driving the vehicle.
The other application I want to describe is an artificial heart pump developed jointly by workers at the Harry Diamond Laboratories and the Walter Reed Army Institute of Research. This device uses a fluid amplifier of the wall-locking type with air as the working fluid.
The rising air pressure in the chamber squeezes the ventricle and thus forces blood through a valve into the circulatory system of the patient.
In effect it acts like the systolic contraction of the heart. After the ventricle has contracted to a certain volume, the air pressure in the chamber opens a port through which the air then escapes and returns to the place where the power stream is flowing toward the splitter.
Hitting the power stream from the side, the returning air causes the stream to switch from the original channel to the opposite channel. This results in a pressure drop in the chamber containing the ventricle; the ventricle therefore begins to expand under the weight of blood that is now able to flow in by gravity through an inlet valve at the top.
He has won eight of his past nine fights and finds himself in his first headlining bout.
Meanwhile a control valve on the other side of the main stream in the amplifier is feeding in a certain amount of airflow to prevent the pressure from falling too low. By the time the ventricle has expanded to its full volume this valve admits a flow of air sufficient to switch the main stream back to the original channel, and so the cycle begins again.
The valve admitting air from the side is, of course, the device that controls the duration of the heart pulse. Another valve in the channel on the same side of the splitter controls the rate of the pulse, and the valve that admits the main stream controls the amplitude of the systolic beat.
All these controls are adjusted beforehand so that the pump supplies blood at the rate and in the amount the patient requires. The models built so far are capable of producing blood pressures of up to about millimeters of mercury and blood flows of up to 10 liters per minute. They can maintain pulse rates within a wide range, from as low as 30 to as high as counts per minute.