EFFECT OF BAFFLES ON SLOSHING MODULATED FORCES AND TORQUES DISTURBANCES REACTED TO GRAVITY GRADIENT DOMINATED ACCELERATIONS

1996 ◽  
Vol 20 (2) ◽  
pp. 187-202
Author(s):  
R.J. Hung ◽  
H.L. Pan ◽  
Y.T. Long
Keyword(s):  
Surface Tension Force ◽  
Viscous Force ◽  
Gravity Gradient ◽  
Tidal Motion ◽  
Damping Effect ◽  
Solid Interface ◽  
Fluid Systems ◽  
Sloshing Dynamics ◽  
Gravity Probe ◽  
Liquid Vapor

The behavior of sloshing dynamics modulated fluid systems driven by the orbital accelerations including gravity gradient and jitter accelerations have been studied. Partially liquid-filled rotating dewar applicable to a full-scale Gravity Probe-B Spacecraft container with and without baffle are considered. Results show that slosh waves excited along the liquid-vapor interface induced by gravity gradient dominated orbital accelerations provide torsional moment with tidal motion of bubble oscillations in the rotating dewar. Fluctuations of slosh reaction forces and torques exerted on the dewar wall driven by the orbital accelerations are also investigated. Since the viscous force between a liquid-solid interface, and the surface tension force between a liquid-vapor-solid interface can greatly contribute to the damping effect of slosh wave excitation, a rotating dewar with baffle provides more areas of liquid-solid and liquid-vapor-solid interfaces than that of rotating Dewar without the baffle. Results show that the damping effect provided by baffle reduces the amplitudes of slosh reactions forces and torques feedback from the fluids to the container, in particular, the components of fluctuations transverse to the direction of baffle.

Effect of the Baffle on the Asymmetric Gravity-Jitter Excited Slosh Wave and Spacecraft Moment and Angular Momentum Fluctuations

1993 ◽  
Vol 207 (2) ◽  
pp. 105-120
Author(s):  
R J Hung ◽  
C C Lee ◽  
F W Leslie
Keyword(s):  
Angular Momentum ◽  
Dynamic Behaviour ◽  
Time Dependent ◽  
Viscous Force ◽  
Wave Excitation ◽  
Rotating Fluids ◽  
Damping Effect ◽  
Solid Interface ◽  
Interface Geometry ◽  
Effect Of Surface

The dynamic behaviour of fluids affected by asymmetric gravity jitter oscillations, in particular the effect of surface tension on partially-filled rotating fluids in a dewar tank, with and without installing baffle-board, imposed by time-dependent directions of background gravity have been investigated. Results show that lower frequency gravity jitter imposed on the time-dependent variations of the direction of background gravity induced a greater amplitude of oscillations and a stronger degree of asymmetry in liquid–vapour interface geometry than that made by the higher frequency gravity jitter. As the viscous force, between liquid and solid interface, greatly contributes to the damping effect of slosh wave excitation, a rotating dewar installed with baffles provides more area of liquid-solid interface than a rotating dewar without baffles. Results show that the damping effect provided by the baffles reduce the amplitude of slosh wave excitation, lowers the degree of asymmetry in the liquid–vapour distribution, and lowers angular momentum and fluid moment fluctuations.

Large Eddy Simulation of Two-Phase Flow Pattern and Transformation Characteristics of Flow Mixing Nozzle

2019 ◽  
Vol 35 (5) ◽  
pp. 693-704
Author(s):  
Jin Zhao ◽  
Zhi Ning ◽  
Ming Lü
Keyword(s):  
Flow Pattern ◽  
Two Phase Flow ◽  
Velocity Ratio ◽  
Inertial Force ◽  
Surface Tension Force ◽  
Viscous Force ◽  
Phase Flow ◽  
Two Phase ◽  
Jet Breakup ◽  
Flow Mixing

ABSTRACTThe two-phase flow pattern of a flow mixing nozzle plays an important role in jet breakup and atomization. However, the flow pattern of this nozzle and its transformation characteristics are still unclear. A diesel-air injection simulation model of a flow mixing nozzle is established. Then the two-phase flow pattern and transformation characteristics of the flow mixing nozzle is studied using a numerical simulation method. The effect of the air-diesel velocity ratio, ratio of the distance between the tube orifice and nozzle hole and the tube diameter (H/D), and the diesel inlet velocity was studied in terms of the jet breakup diameter (jet diameter at the breakup position) and jet breakup length (length of the diesel jet from the breakup position to the nozzle outlet). The results show that the jet breakup diameter decreases with the decrease in H/D or the increase in the air-diesel velocity ratio and diesel inlet velocity. The jet breakup length increases first and then decreases with the increase in H/D and air-diesel velocity ratio; the trend of the diesel inlet velocity is complicated. In addition, a change in the working conditions also causes some morphological changes that cannot be quantitatively analyzed in the diesel-air flow pattern. The transition characteristics of the flow pattern are analyzed, and it is found that the main reason for the change in the flow pattern is the change in the inertial force of the air, surface tension force, and viscous force of diesel (non-dimensional Reynolds number and Weber number describe the transition characteristics in this paper). The surface tension force of diesel decreases and the viscous force of diesel and inertial force of air increase when the air-diesel velocity ratio increases or H/D decreases. However, the effects of the diesel surface tension force and viscous force effect are much smaller than that of the air inertial force, which changes the diesel-air flow pattern from a drop pattern to a vibration jet pattern, broken jet pattern, and then a chaotic jet pattern.

Improved Taylor analogy breakup and Clark models for droplet deformation prediction

2017 ◽  
Vol 233 (2) ◽  
pp. 767-775 ◽  
Author(s):  
Zhenlong Wu ◽  
Benyin Lv ◽  
Yihua Cao
Keyword(s):  
Leading Edge ◽  
Surface Tension Force ◽  
Aerodynamic Characteristics ◽  
Viscous Force ◽  
Pressure Force ◽  
Droplet Deformation ◽  
Deformation Prediction ◽  
Clark Model ◽  
Improved Model ◽  
Breakup Model

The deformation of rain droplet at the leading edge of a wing is critical to the aerodynamic characteristics of the aircraft under heavy rainfall and icing conditions. This study introduces the improvement of the Taylor analogy breakup and Clark models for prediction of droplet deformation near the leading edge of an airfoil. The slip velocity is considered as time-variant in the improved Taylor analogy breakup model. The viscous force is optimized in the improved Clark model. The prediction results suggest that the Clark models predict better results than the Taylor analogy breakup models. Besides, the improved Clark model has the highest prediction accuracy. However, considering the Clark model is derived based on a two-dimensional model, even the improved model still has some unavoidable deviations from the real situation. In addition, the simplified surface area in the surface tension force and the approximation of the pressure force in the original Clark model are very effective, thus are kept the same in the improved Clark model.

Development of a New Passive-Active Magnetic Damper for Vibration Suppression

2005 ◽  
Vol 128 (3) ◽  
pp. 318-327 ◽  
Author(s):  
Henry A. Sodano ◽  
Daniel J. Inman ◽  
W. Keith Belvin
Keyword(s):  
Magnetic Field ◽  
Control System ◽  
Eddy Currents ◽  
Vibration Suppression ◽  
Internal Resistance ◽  
Viscous Force ◽  
Damping Force ◽  
Conductive Material ◽  
Damping Effect ◽  
Active Portion

Magnetic fields can be used to apply damping to a vibrating structure. Dampers of this type function through the eddy currents that are generated in a conductive material experiencing a time-changing magnetic field. The density of these currents is directly related to the velocity of the change in magnetic field. However, following the generation of these currents, the internal resistance of the conductor causes them to dissipate into heat. Because a portion of the moving conductor’s kinetic energy is used to generate the eddy currents, which are then dissipated, a damping effect occurs. This damping force can be described as a viscous force due to the dependence on the velocity of the conductor. In a previous study, a permanent magnet was fixed in a location such that the poling axis was perpendicular to the beam’s motion and the radial magnetic flux was used to passively suppress the beam’s vibration. Using this passive damping concept and the idea that the damping force is directly related to the velocity of the conductor, a new passive-active damping mechanism will be created. This new damper will function by allowing the position of the magnet to change relative to the beam and thus allow the net velocity between the two to be maximized and thus the damping force significantly increased. Using this concept, a model of both the passive and active portion of the system will be developed, allowing the beams response to be simulated. To verify the accuracy of this model, experiments will be performed that demonstrate both the accuracy of the model and the effectiveness of this passive-active control system for use in suppressing the transverse vibration of a structure.

scholarly journals Squeezing Dynamic Mechanism of High-Viscosity Droplet and its Application for Adhesive Dispensing in Sub-Nanoliter Resolution

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 728
Author(s):  
Ping Zhu ◽  
Zheng Xu ◽  
Xiaoyu Xu ◽  
Dazhi Wang ◽  
Xiaodong Wang ◽  
...  
Keyword(s):  
Surface Tension ◽  
Contact Force ◽  
Surface Tension Force ◽  
High Viscosity ◽  
Dynamic Mechanism ◽  
Tension Force ◽  
Viscous Force ◽  
Transfer Printing ◽  
Critical Contact ◽  
Printing Method

The dispensing resolution of high-viscosity liquid is essential for adhesive micro-bonding. In comparison with the injection technique, the transfer printing method appears to be promising. Herein, an analytical model was developed to describe the dynamic mechanism of squeezing-and-deforming a viscous droplet between plates in a transfer printing process: as the distance between plates decreases, the main constituents of contact force between the droplet and substrate can be divided into three stages: surface tension force, surface tension force and viscous force, and viscous force. According to the above analysis, the transfer printing method was built up to dispense high-viscosity adhesives, which replaced the geometric parameters, utilized the critical contact force to monitor the adhesive droplet status, and served as the criterion to trigger the liquid-bridge stretching stage. With a home-made device and a simple needle-stamp, the minimum dispensed amount of 0.05 nL (93.93 Pa·s) was achieved. Moreover, both the volume and the contact area of adhesive droplet on the substrate were approximately linear to the critical contact force. The revealed mechanism and proposed method have great potential in micro-assembly and other applications of viscous microfluidics.

Numerical Analysis of Liquid Breakup and Drop Generation in Low Velocity Jets

2015 ◽  
Author(s):  
Sucharitha Rajendran ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
Surface Tension Force ◽  
The Other ◽  
Viscous Force ◽  
Liquid Jet ◽  
Biological Applications ◽  
Liquid Stream ◽  
Low Velocity ◽  
Satellite Drops ◽  
Wide Range

Biological sprays and aerodynamically assisted bio-jets are increasingly employed in treatment of living cells and organisms for applications in regenerative medicine, tissue repair, and advanced therapeutics. The liquid used in biological applications cover a wide range of viscosities and surface tensions. Determining conditions that achieve steady and uniform drop distribution for a range of properties of the liquid jet is critical in advancing biological applications. In this study, numerical simulations of jet breakup are carried out using a modified volume of fluid (VOF) approach to capture the interface. The interplay of viscosity and surface tension is studied by varying liquid properties. Simulations show that a high viscosity jet stretches and elongates before a liquid segment detaches. Based on the thickness of the liquid thread connecting the detaching drop to the main liquid stream, two fundamentally different modes of liquid pinch off have been predicted: thick-thin and thin-thick. In the thick-thin mode, the liquid jet has a growing drop at its edge. As this drop grows in size, the liquid stream stretches till the drop is pinched off the liquid stream. In the other mode in addition to the pinch off of drops from the jet, ligaments of liquid break off. The change in the breakup mode is primarily governed by the relative magnitude of the viscous force compared to surface tension with high viscous force leading to thin-thick liquid stretching and pinch off. Thick-thin stretching is seen to produce slow moving satellite drops that merge backwards with the oncoming drop, while thin-thick stretching is noticed to result in faster satellite drops that merge forwards. On the other hand when surface tension force dominates, non-merging satellite drops are formed that move with a speed close to the primary drops.

Dynamics of Droplet Deformation in Microchannels With Symmetric and Asymmetric Constrictions

2017 ◽  
Author(s):  
Binita Nath ◽  
Manash Pratim Borthakur ◽  
Gautam Biswas ◽  
Amaresh Dalal
Keyword(s):  
Capillary Number ◽  
Viscosity Ratio ◽  
Surface Tension Force ◽  
Viscous Force ◽  
Channel Height ◽  
Drop Diameter ◽  
Immiscible Fluid ◽  
Droplet Deformation ◽  
Flow Solver ◽  
Micro Channels

The investigation of the dynamics of a droplet traversing through constricted channels is an interesting field of research. In the present work, the motion and deformation of a neutrally buoyant droplet in planar constricted micro channels containing another immiscible fluid is studied computationally using an open-source finite-volume fluid flow solver, Gerris. The important non-dimensional parameters pertaining to such type of flow are — the Capillary number, which gives the relative importance of the viscous force over the surface tension force, the viscosity ratio between the dispersed and suspending medium and the ratio of the drop diameter to the channel height. Both symmetrical and asymmetrical constrictions are considered and results obtained are compared with a straight channel without any constriction. The parametric studies are conducted to study the effect of droplet size, viscosity ratio, Capillary number and presence of constriction in the channel. Depending on the parameters chosen, the drop extends to a maximum length as its front passes through the constriction and the deformation increases with the increase in number of constrictions. In the case of large drops, it is observed that the droplet disintegration rate increases in the presence of constrictions.

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