Showing papers on "Slip ratio published in 1982"

Influence of the velocity ratio on the spatial instability of mixing layers

Abstract: The linear spatial instability of the tanh and Blasius mixing layers is studied for different values of the ratio between the difference and the sum of the velocities of the two co‐flowing streams. The growth rate, phase velocity, and perturbation velocity distributions are determined numerically and the results are compared with expansions for small shear or low frequency. It is found that the maximum growth rate is approximately proportional to the velocity ratio. This is shown to be consistent with the observed variation of shear layer spreading rate with velocity ratio and with a recent model of flight effects on jet mixing noise.

Three-dimensional finite difference simulation of fault dynamics: Rectangular faults with fixed rupture velocity

Abstract: We analyze three-dimensional finite difference solutions for a simple shear-crack model of faulting to determine the effects of fault length and width on the earthquake slip function. The fault model is dynamic, with only rupture velocity, fault dimensions, and dynamic stress-drop prescribed. The numerical solutions are accurate for frequencies up to 5 Hz, and are combined with asymptotic results for shear cracks in order to characterize the slip function at higher frequencies. Near the hypocenter, the slip velocity exhibits a square-root singularity whose intensity increases with hypocentral distance. At distances greater than the fault width, w , growth of the velocity intensity ceases, and the slip function becomes nearly invariant with distance along the fault length. Closed-form expressions are developed for the dependence of static slip ( s ∞), slip rise time ( TR ), and slip velocity intensity ( V ) on fault geometry. Along the center line of a long, narrow fault, at hypocentral distances exceeding w , these expressions reduce to s ∞ ≈ w Δτ/μ, TR ≈ 0.5 w/vR , and V ≈ √ w /2 vR Δτ/μ, where Δτ is the dynamic stress drop, μ the shear modulus, and vR the rupture velocity. The numerical results imply that uniform-dislocation kinematic earthquake models in which slip is represented by a ramp time function will underpredict high-frequency ground motion relative to low-frequency ground motion. A further implication of the numerical solutions is that the nature of inelastic processes at the advancing edge of a long fault will depend on fault width, but will be independent of rupture length.

Boundary layer flow of a dusty fluid over a semi-infinite flat plate

Abstract: Both the drag force due to slip and the transverse force due to slip-shear have been considered in boundary layer equations. The solution has been found in a power series of non-dimensionalx, x being the distance in the down-stream direction. Solutions for high slip region and small slip region characterised byx≪1 andx≫1 respectively, have been found separately. In the high slip region the effect of increase in concentration parameter α of the dust particles is to increase the magnitude of the longitudinal fluid phase velocityu. Also the magnitude of the longitudinal particle slip velocityup-u is becoming maximum on the plate and decreasing along the plate withx. The transverse particle velocityvp is independent of α but it is directly proportional to β, the transverse force coefficient. An interesting result is thatvp is assuming small positive value on the plate. The transverse force has taken an important role in migration of particles away from the plate. In the small slip region the flow of dust particles is mainly governed by the fluid-phase. The effect of α on the flow field in this region is to decrease the boundary layer thickness. In this region the particles are having some tendency to accumulate near the plate. Lastly, it has been found that the shearing stress, skinfriction and the dimensionless drag-coefficient on the plate increase with increase of α.

Flow-Induced Vibration of Tube Arrays With Various Pitch-to-Diameter Ratios

Abstract: Tube arrays in cross flow start to vibrate abruptly when the flow reaches at a certain velocity. The threshold flow velocity depends upon the geometrical arrangement of tubes. It is very important for practical applications to understand the relations between the threshold velocity and pitch-to-diameter ratio of tube array. Unsteady fluid dynamic forces on a tube array with a pitch-to-diameter ratio of 2.0 were clarified experimentally and the characteristics of the threshold velocity were revealed by calculating the velocity with the unsteady forces. By comparing the threshold velocities of tube arrays of pitch-to-diameter ratio of 2.0 and 1.33, the characteristics of threshold velocity with respect to pitch-to-diameter ratio were clarified.

Slip preventive device for wheel

Abstract: PURPOSE:To allow a stable and optimum acceleration as well as improvement in the fuel economy by providing a driven wheel speed sensor to a driven wheel, a drive wheel sensor to a drive wheel and a control device which controls the driving torque of an automobile in response to the slip ratio. CONSTITUTION:A driven wheel speed sensor 2 is provided to a driven wheel, and a drive wheel speed sensor 4 to a drive wheel. A control unit 8 computes the outputs from both sensors 2, 4 to calculate the slip ratio, and in response to a change in this slip ratio, a DC motor 12 is operated to throttle a throttle valve 11 to reduce the flow rate of a mixture to an engine E. By this constitution, the tire traction is utilized to the maximum extent to obtain a stabilized acceleration performance. Also, handling at the time of acceleration is improved, and the fuel economy is improved.

On slip effect in free coating of non-Newtonian fluids

Abstract: The failure of the current theories to predict the coating thickness of non-Newtonian fluids in free coating operations is shown to be a result of the effective slip at the moving rigid surface being coated. This slip phenomenon is a consequence of stress induced diffusion occurring in flow of structured liquids in non-homogeneous flow fields. Literature data have been analysed to substantiate the slip hypothesis proposed in this work. The experimentally observed coating thickness is shown to lie between an upper bound, which is estimated by a no-slip condition for homogeneous solution and a lower bound, which is estimated by using solvent properties. Some design considerations have been provided, which will serve as useful guidelines for estimating coating thickness in industrial practice.

Antiskid control circuit

Abstract: PURPOSE:To obtain proper control of slip even if an approximate car body speed is different from a true car body speed by providing a discriminator to decide whether wheels are under control or not and a switch signal generator for reducing the reference slip ratio at a fixed condition CONSTITUTION:A control circuit 7 is operated by a slip signal lambda from a slip computation comparator 6 operated on the basis of a deceleration signal -b and an acceleration signal +b from an acceleration and deceleration computation comparator 3 and the highest speed selected by a selection circuit 5, that is, an approximate car body speed In the slip computation circuit 6, the signal obtained by multiplying the approximate car body speed by a slip ratio is compared with a wheel speed ratio A discriminator 8 decides whether wheels are under control or not, while a switch signal generator 15 issues a signal when the speed difference surpasses a fixed value These signals reduce the reference value of the slip ratio in the slip computation comparator 6 via an AND gate 9 and an OR gate 10

Driving power transmission of paused cylinder engine

Abstract: PURPOSE:To prevent a fluctuation in torque from being transmitted toward a transmission by controlling a slip ratio of a direct driver clutch at cylinder pause operation greater than a slip ratio produced at an all-cylinder operation. CONSTITUTION:If an operation to produce a certain difference between revolution speeds of a crankshaft 3 of an engine 1 and an output shaft 4 toward a transmission 2 is required due to a fluctuation in torque, a computer 23 generates a duty control instruction to a solenoid valve 22 according to an input element groups. A pressure of oil in an oil pressure passage 31 is thereby changed and a pressure oil from an oil pressure supply system is sent from an oil pressure passage 35 into an oil pressure passage 32 through an oil pressure chamber 26. A resultant reduction in revolution speed of the crankshaft 3 of the engine 1 is detected and based on the detection, a cylinder pause operation instruction is issued from the computer 23 to the engine along with a cylinder pause operation time control instruction to a solenoid valve 22 for making a slip ratio of a direct drive clutch 6 greater than that at an all-cylinder operation time.

Evaluation of winter-driving traction aids

Abstract: A set of test procedures has been selected to measure the braking, driving traction, and controllability of (1) vehicles fitted with tires and tire-associated traction aids intended to increase available friction on ice and snow surfaces and (2) vehicles fitted with drive-train aids intended to make better use of available friction The performance of traction-aids intended to increase available friction, such as tire chains, snow tires, studded tires, and improved rubber compounds, may be determined from a combination of the following test data: 1 Locked-wheel braking friction or locked-wheel stopping distance at a speed of 20 mph (324 km/hr) 2 Spinning driving traction at a vehicle speed of 5 mph (81 km/hr) with the traction force measured at a slip ratio greater than 1 3 Spinning driving traction with the test vehicle stationary and tire slip speed greater than 10 mph (162 km/hr); and 4 Limiting (minimum) lateral tire force measured with a single-wheel tester The standardized test procedures for obtaining the test data are described in the report The performance of traction-aids intended to make better use of available friction, such as the limited slip differential, nonlocking brakes, and the four-wheel drive, may often be calculated directly from the relevant vehicle characteristics and an assumed tire/friction factor A simulation program was written and used to study the controllability performance of vehicles fitted with these aids (Author)

An Experimental Study on Propeller Air Ventilation and Its Induced Vibratory Forces

Abstract: As well known, the screw propeller immersed near the water surface ventilates air through the free surface. This phenomenon itself has been well investigated in the past. However there are few reports which examined the propeller vibratory forces induced by this air ventilation phenomenon. This paper investigates experimentally the propeller bearing forces due to the air ventilation according to the open propeller dynamometer. The experimental results reveal the followings. The manifestation of the air ventilation can be classified into the partial ventilation and the super ventilation. When the former occurs, the bearing forces are induced. The value of the bearing force is influenced by the main factors of immersion depth, slip ratio, and free surface behaviour. As for the slip ratio, the bearing forces are likely to decrease with the decrease of the slip ratio and tend to zero in the region under the critical slip ratio, of which value is 0.3-0.4 for the model screw propellers used in this experiments, where the air ventilation does not occur. It is noticeable that the bearing forces due to the air ventilation are considerably greater than that due to the shear flow of hull wake. Therefore the engineer designing the propeller shaft systems needs to consider the effects of the bearing forces induced by the air ventilation.

Controller of variable damper of motor car

Abstract: PURPOSE:To prevent a squatting phenomenon from occurring, by so constituting that a squat state is decided by obtaining a slip ratio through speeds of a driving component and a component to be driven and enhancing the attenuation force of a variable damper, in the titled device for adjusting attenuation force of a suspension device. CONSTITUTION:Respective outputs of an engine speed sensor 24 and a car speed sensor 25 are applied to a comparator 31 through an amplifier 30 to be amplified by a Schmitt circuit 26, a converter 27, a Schmitt circuit 28, a converter 29 and a gear ratio. A solenoid 22 for control of an operation rod of a variable damper not illustrated is turned ON, the operation of rod of the variable damper is moved up and down and attenuation force of the variable damper is made variable by the comparator 31 through a driving circit 32 by applying an H level signal by deciding that a slip ratio is high when an engine speed is larger than a value to be obtained by multiplying a car speed 25 by a gear ratio. With this constitution, anti-squat control of a vehicle is made and a squatting phenomenon can be prevented from occurring.

Holographic and photographic studies of high‐quality steam‐water critical flow

Abstract: High-quality (95%) steam-water critical flow through a straight pipe was studied using high-speed photographic and holographic techniques. The results indicate that most of the water exists as a discontinuous or continuous thin film which flows along the wall with a speed much slower than that of the steam. This results in slip ratios higher than those reported before. Although a separated flow model would seem to describe the actual flow situation more closely than other models, the assumption of thermal equilibrium between phases and the fact that the flow is not separated except close to the exit plane are probably explanations for differences in slip ratios obtained in this study from those predicted.

Slip prevention device for wheel

Abstract: PURPOSE:To prevent an engine from stopping when a motor-cycle body is jumped up, etc., by providing a sensor for the hull expansion of a driving-wheel suspension of a motor-cycle, etc., and stopping the operation of a carburetor control circuit based on the slip ratio of the driving wheel by means of the output of said sensor. CONSTITUTION:When driving a motor-cycle, signals proportional to the number of revolution of the corresponding wheels are outputted from speed sensors 2, 4 provided on each wheel shaft part 1a, 3a of front and rear wheels 1, 3, and the slip ratio of the rear wheel, i.e., a driving wheel 3, is calculated from both of these signals at a control unit (figure omitted) provided on the motor-cycle. In accordance with this slip ratio, the amount and direction of electricity to be applied to a motor 17 are controlled in a carburetor 19, thereby controlling the area of the opening of a main jet 16 through a needle 22. In this case, if a motor-cycle body jumps causing a rear suspension 15 to be fully expanded, and when a full-expansion sensor 10 is turned off, the slip prevention controlling action by means of said control unit is stopped, controlling the opening of the carburetor only by the operation of a throttle.

Vehicle speed controller for agricultural vehicle etc

Abstract: PURPOSE:To simply obtain optimum creep rate by means of integrating the vehicle so as to be able to make creep running (super-slow speed running) spplying slip operation of a friction clutch which can control slip ratio through hydraulic action CONSTITUTION:The engine and the driving gear between rear wheels provide a main mechanical clutch 3 on the transmission shaft 4, the structure is integrated by installing a friction clutch 6 at the leading edge of a hollow transmission shaft 5 which is externally inserted on the transmission shaft 4, and the both shafts 4, 5 are connected with the friction clutch 6 This friction clutch 6 is integrated in such a way that a piston 47 is moved backward by means of oil pressure which is fed through an oil path 50 into an oil chamber 49, and a sliding fittings 40 are moved backward against a spring 46, by which clutch engagement is released, and slip operation is properly made by properly controlling oil pressure to be worked to the oil chamber 49 This slip operation state is made available when the speed change gear is at the first speed change stage

An Experimental and Analytical Study on Spray Flow Field by Liquid/Gas Coaxial Injector Elements(1)

Abstract: The concentric-tube injector element has been used extensively in liquid-gas injectors, such as liquid oxygen-hydrogen rocket injectors. To predict the combustion performance and heat flux distribution along a combustion chamber with a coaxial injector, a good understanding of the spray flow field as it concerns the atomization rate of the liquid jet by the high velocity gas flow and the mixing process of liquid droplets with the gas flow, is of critical importance. In this report the spray flow field formed by flush-face concentric-tube injector elements was extensively investigated by non-reactive cold liquid-gas flow test. And also an analytical model was derived to predict the spray flow field, including the local atomization rate of the liquid jet, the gas-phase velocity decay, liquid mass flux dispersion and the local liquid-droplets to gas mixing efficiencies. By this study it was shown that the ratio of the half-width of the liquid phase mass flux to that of the gas phase velocity is the critical factor in controlling the mixing efficiencies of the spray flow field; in addition, this critical factor is related to the ratio of the gas to liquid injection velocity.