Analytical simulation of influential parameters affecting grooved wet clutches performance underdisengagement condition

2021 ◽  
pp. 135065012110477
Author(s):  
Hossein Nasiri ◽  
Cristiana Delprete ◽  
Eugenio Brusa ◽  
Abbas Razavykia ◽  
Alireza Esmaeilzadeh
Keyword(s):  
Pressure Gradient ◽  
Rotational Speed ◽  
Power Transmission ◽  
Stokes Equations ◽  
Rotational Velocity ◽  
Outer Radius ◽  
Drag Torque ◽  
Physical Relation ◽  
Critical Rotational Speed ◽  
Analytical Relations

Innovating new approaches and effective methods to improve the efficiency of mechanical systems in terms of energy losses and environmental effects serve as an attractive domain for researchers and industries. Wet clutches are widely used in power transmission systems in automotive and other tribological mechanisms. The wet clutch has two functional modes; under the engaged state, in which two disks come into contact to each other, and under disengagement the plates are located at a very short distance from each other, and oil flows between them. In disengaged state, the differential speed of driving and driven units causes oil shearing within the clearance which leads to transmission of certain amount of drag torque from the driving to the output shaft. This transferred drag torque is distinguished as power loss in form of heat. The governing physical relation based on continuity equation and Navier–Stokes equations reveals that in a certain rotational velocity, the pressure gradient at the outer radius of the clutch becomes null, and, in this circumstance, aeration occurs that is known as critical rotation speed. Experimental findings provide evidence that geometry manipulation and considering grooves over the frictional disk, reduces the critical rotational speed. But there is a shortage of physical analytical relations to predict the pressure gradient in grooved wet clutches. Therefore, this article is aimed to introduce analytical model to evaluate grooved wet clutches performance in terms of drag torque and critical rotational speed under single-phase flow condition.

Numerical Study of the Laminar Flow Past a Rotating Square Cylinder at Low Spinning Rates

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Dipankar Chatterjee ◽  
Satish Kumar Gupta
Keyword(s):  
Rotational Speed ◽  
Stream Flow ◽  
Free Stream ◽  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Low Frequency ◽  
Square Cylinder ◽  
Rotating Circular Cylinder ◽  
Critical Rotational Speed

The fluid dynamic interaction between a uniform free stream flow and the rotation induced flow from a sharp edged body is numerically investigated. A two-dimensional (2D) finite volume based computation is performed in this regard to simulate the laminar fluid flow around a rotating square cylinder in an unconfined medium. Body fitted grid system along with moving boundaries is used to obtain the numerical solution of the incompressible Navier–Stokes equations. The Reynolds number based on the free stream flow is kept in the range 10≤Re≤200 with a dimensionless rotational speed of the cylinder in the range 0≤Ω≤5. At low Re=10, the flow field remains steady irrespective of the rotational speed. For 50≤Re≤200, regular low frequency Kármán vortex shedding (VS) is observed up to a critical rate of rotation (Ωcr). Beyond Ωcr, the global flow shows steady nature, although high frequency oscillations in the aerodynamic coefficients are present. The rotating circular cylinder also shows likewise degeneration of Kármán VS at some critical rotational speed. However, significant differences can be seen at higher rotation. Such fluid dynamic transport around a spinning square in an unconfined free stream flow is reported for the first time.

Direct simulation of transition in an oscillatory boundary layer

1998 ◽  
Vol 371 ◽  
pp. 207-232 ◽  
Author(s):  
G. VITTORI ◽  
R. VERZICCO
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Turbulent Regime ◽  
Two Dimensional ◽  
Temporal Development ◽  
Direct Simulation ◽  
Navier Stokes Equations ◽  
Oscillatory Boundary Layer

Numerical simulations of Navier–Stokes equations are performed to study the flow originated by an oscillating pressure gradient close to a wall characterized by small imperfections. The scenario of transition from the laminar to the turbulent regime is investigated and the results are interpreted in the light of existing analytical theories. The ‘disturbed-laminar’ and the ‘intermittently turbulent’ regimes detected experimentally are reproduced by the present simulations. Moreover it is found that imperfections of the wall are of fundamental importance in causing the growth of two-dimensional disturbances which in turn trigger turbulence in the Stokes boundary layer. Finally, in the intermittently turbulent regime, a description is given of the temporal development of turbulence characteristics.

Measurements of Apparent Mass Torque Coefficients of Two-Dimensional Centrifugal Impellers

1986 ◽  
Vol 108 (4) ◽  
pp. 407-413
Author(s):  
Y. Tsujimoto ◽  
K. Imaichi ◽  
T. Moritani ◽  
K. Kim
Keyword(s):  
Angular Velocity ◽  
Flow Rate ◽  
Potential Flow ◽  
Rotational Velocity ◽  
Apparent Mass ◽  
Two Dimensional ◽  
Drag Torque ◽  
Mean Flow ◽  
Experimental Values

Apparent mass torque coefficients for fluctuations of flow rate and angular velocity are determined experimentally for two-dimensional centrifugal impellers. Nearly sinusoidal fluctuations of flow rate and angular velocity are produced by using crank mechanisms, and the resulting unsteady torque on the impeller is measured. The torque is divided into components in-phase and out-of-phase with the displacements. The in-phase components are used to determine the apparent mass coefficients. Drag torque coefficients are defined and used to represent the out-of-phase components. The tests are conducted under various frequencies and amplitudes of the fluctuations with zero mean flow rate and rotational velocity. The apparent mass torque coefficients are compared with theoretical values obtained under the assumption of a two-dimensional potential flow. The experimental values are 5 to 20 percent larger than the theoretical ones and no appreciable effects of the frequency and the amplitude are observed within the range of the experiments.

Analysis of Torsional Stick-Slip Situations from Recorded Downhole Rotational Speed Measurements

2021 ◽  
pp. 1-15
Author(s):  
Eric Cayeux ◽  
Adrian Ambrus ◽  
Lars Øy ◽  
Arvid Helleland ◽  
Svein Brundtland ◽  
...  
Keyword(s):  
Rotational Speed ◽  
Rotational Velocity ◽  
The Other ◽  
Drilling Process ◽  
Stick Slip ◽  
Torsional Oscillations ◽  
Direct Observations ◽  
New Information ◽  
Weight On Bit ◽  
Downhole Measurements

Summary The use of recorded downhole rotational speed measurements with a bandwidth up to 9 Hz gives new insights into the conditions under which stick-slip torsional oscillations occur. Observations made while drilling two reservoir sections have shown that, out of all the stick-slip situations identified, 72% of them for one well and 64% for the other well occurred in off-bottom conditions. In these off-bottom conditions, stick-slip was systematically observed while starting the topdrive (TD) until a sufficiently high TD rotational velocity was requested. For these two sections, off-bottomstick-slip was either related to using TD speeds below 120 rev/min or to reaming down during reciprocation procedures. In on-bottom conditions, stick-slip events occurred predominantly when the TD speed was less than 120 rev/min (53 and 32% of the on-bottom cases) but also in association with downlinking to the rotary steerable system (RSS) (23 and 46% of the on-bottom cases), and this, even though the TD speed was larger than 120 rev/min. These on-bottomstick-slip situations did not necessarily occur at a very high weight on bit (WOB) because 98% of them for one well and 46% for the other well took place when the WOB was lower than 10 ton. Downhole measurements have shown that when the drillstring is subject to strong stick-slip conditions, the downhole rotational speed changes from stationary to more than 300 rev/min in just a fraction of a second. Direct observations of downhole rotational speed at high frequency help in discovering conditions that were not suspected to lead to large torsional oscillations. This new information can be used to improve drilling operational procedures and models of the drilling process, therefore enabling increased drilling efficiency.

scholarly journals Direct numerical simulation of conical shock wave–turbulent boundary layer interaction

2019 ◽  
Vol 877 ◽  
pp. 167-195 ◽  
Author(s):  
Feng-Yuan Zuo ◽  
Antonio Memmolo ◽  
Guo-ping Huang ◽  
Sergio Pirozzoli
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Shock Wave ◽  
Turbulent Boundary Layer ◽  
Direct Numerical Simulation ◽  
Pressure Gradient ◽  
Stokes Equations ◽  
Shear Stresses ◽  
Mean Flow ◽  
Conical Shock

Direct numerical simulation of the Navier–Stokes equations is carried out to investigate the interaction of a conical shock wave with a turbulent boundary layer developing over a flat plate at free-stream Mach number $M_{\infty }=2.05$ and Reynolds number $Re_{\unicode[STIX]{x1D703}}\approx 630$, based on the upstream boundary layer momentum thickness. The shock is generated by a circular cone with half opening angle $\unicode[STIX]{x1D703}_{c}=25^{\circ }$. As found in experiments, the wall pressure exhibits a distinctive N-wave signature, with a sharp peak right past the precursor shock generated at the cone apex, followed by an extended zone with favourable pressure gradient, and terminated by the trailing shock associated with recompression in the wake of the cone. The boundary layer behaviour is strongly affected by the imposed pressure gradient. Streaks are suppressed in adverse pressure gradient (APG) zones, but re-form rapidly in downstream favourable pressure gradient (FPG) zones. Three-dimensional mean flow separation is only observed in the first APG region associated with the formation of a horseshoe vortex, whereas the second APG region features an incipient detachment state, with scattered spots of instantaneous reversed flow. As found in canonical geometrically two-dimensional wedge-generated shock–boundary layer interactions, different amplification of the turbulent stress components is observed through the interacting shock system, with approach to an isotropic state in APG regions, and to a two-component anisotropic state in FPG. The general adequacy of the Boussinesq hypothesis is found to predict the spatial organization of the turbulent shear stresses, although different eddy viscosities should be used for each component, as in tensor eddy-viscosity models, or in full Reynolds stress closures.

An Innovative Micro Control System for Quasi-Continuous Power Transmission Systems (QCPTS)

2008 ◽  
Author(s):  
Asghar Nasr ◽  
Yaser Jafari Jozani ◽  
Mohsen Ghazvini
Keyword(s):  
Control System ◽  
Power Transmission ◽  
Low Cost ◽  
Rotational Velocity ◽  
Transmission Systems ◽  
Velocity Change ◽  
Velocity Sensor ◽  
Power Transmission Systems ◽  
Electric Traction ◽  
Continuous Power

Ordinary stepped power transmission systems that used in industry, exhibit abundant energy dissipation, complicated handling and costly maintenance. On the other hand, continuously-variable power transmissions (CVTs), which are recently considered to be used in the industry, despite their high capabilities, face a number of drawbacks including such as : limited torque transmission capacity, high-precision manufacturing and installation requirements, low cost effectiveness and relatively modest power transmission efficiencies. Therefore, innovative power transmission systems that intend to resolve or lessen one or more of these disadvantages are critical in power transmission from pinion to wheel in electric traction motors (motors) of both diesel and electric locomotives; especially when active and advanced control of traction effort and adhesion is of high importance and are going to be welcomed by rail industries. The controlling subsystem of QCPTS includes a micro control system consisting of rotational velocity sensor, power supplier source, and intelligent pins. In each rotational velocity range the velocity sensor sends a signal to the micro controller for processing which causes one intelligent pins become activated and the previously activated pin become deactivated simultaneously. As a result, depending on the rotational velocity change of the rotating output shaft the QCPTS engages a pair of gears. The intelligent magnetic pins have two Start and End work stations. The Start station activates the gear by receiving a starting signal from micro controller and also the End station deactivates the gear by receiving the End signal from micro.

scholarly journals Disentangling rotational velocity distribution of stars

2016 ◽  
Vol 12 (S329) ◽  
pp. 393-393
Author(s):  
Michel Curé ◽  
Diego F. Rial ◽  
Julia Cassetti ◽  
Alejandra Christen
Keyword(s):  
Distribution Function ◽  
Rotational Speed ◽  
Cumulative Distribution Function ◽  
Binary Systems ◽  
Extrasolar Planets ◽  
Rotational Velocity ◽  
Cumulative Distribution ◽  
Tikhonov Regularization Method ◽  
Standard Assumption ◽  
Ratio Distribution

AbstractRotational speed is an important physical parameter of stars: knowing the distribution of stellar rotational velocities is essential for understanding stellar evolution. However, rotational speed cannot be measured directly and is instead the convolution between the rotational speed and the sine of the inclination angle vsin(i). The problem itself can be described via a Fredhoml integral of the first kind. A new method (Curé et al. 2014) to deconvolve this inverse problem and obtain the cumulative distribution function for stellar rotational velocities is based on the work of Chandrasekhar & Münch (1950). Another method to obtain the probability distribution function is Tikhonov regularization method (Christen et al. 2016). The proposed methods can be also applied to the mass ratio distribution of extrasolar planets and brown dwarfs (in binary systems, Curé et al. 2015).For stars in a cluster, where all members are gravitationally bounded, the standard assumption that rotational axes are uniform distributed over the sphere is questionable. On the basis of the proposed techniques a simple approach to model this anisotropy of rotational axes has been developed with the possibility to “disentangling” simultaneously both the rotational speed distribution and the orientation of rotational axes.

Exact Solution of the Navier-Stokes Equations for the Fully Developed, Pulsating Flow in a Rectangular Duct With a Constant Cross-Sectional Velocity1

2003 ◽  
Vol 125 (2) ◽  
pp. 382-385 ◽  
Author(s):  
S. Tsangaris ◽  
N. W. Vlachakis
Keyword(s):  
Pressure Gradient ◽  
Stokes Equations ◽  
Rectangular Cross Section ◽  
Gradient Flow ◽  
Pulsating Flow ◽  
Artificial Kidney ◽  
Navier Stokes ◽  
Rectangular Duct ◽  
Cross Sectional ◽  
Navier Stokes Equations

The Navier-Stokes equations have been solved in order to obtain an analytical solution of the fully developed laminar flow in a duct having a rectangular cross section with two opposite equally porous walls. We obtained solutions both for the case of steady flow as well as for the case of oscillating pressure gradient flow. The pulsating flow is obtained by the superposition of the steady and oscillating pressure gradient solutions. The solution has applications for blood flow in fiber membranes used for the artificial kidney.

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