Modeling of drop deformation in proximity to an airfoil

2018 ◽  
Vol 233 (5) ◽  
pp. 1655-1659
Author(s):  
Zhenlong Wu ◽  
Benyin Lv ◽  
Yihua Cao
Keyword(s):  
Prediction Accuracy ◽  
Slip Velocity ◽  
Surface Tension Force ◽  
Viscous Force ◽  
Shape Deformation ◽  
Drop Deformation ◽  
Force Term ◽  
Single Drop ◽  
Clark Model ◽  
Improved Model

In this paper, an analytical model is improved to predict the shape deformation of a single drop in proximity to an airfoil on the basis of the Clark model. The model was optimized through the adjustment of the viscous force, surface tension force term, and slip velocity. The performance and applicability of the improved model is tested against the published experimental data and discussed. The prediction accuracy is significantly enhanced with the relative error reduced from above 20% to below 5%, almost reaching an equivalent level to the excellent droplet ratio deformation (DRD) model proposed by others previously.

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.

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.

A Viscoelastic VOF-PROST Code for the Study of Drop Deformation

Volume 3 ◽  
2004 ◽  
Author(s):  
Y. Renardy ◽  
M. Renardy ◽  
T. Chinyoka ◽  
D. B. Khismatullin ◽  
J. Li
Keyword(s):  
Surface Tension ◽  
Constitutive Equation ◽  
Viscoelastic Medium ◽  
Three Dimensional ◽  
Surface Tension Force ◽  
Volume Of Fluid ◽  
Tension Force ◽  
Drop Deformation ◽  
Volume Of Fluid Method ◽  
Viscoelastic Liquids

A volume of fluid method is developed with a parabolic representation of the interface for the surface tension force (VOF-PROST). This three-dimensional transient code is extended to treat viscoelastic liquids with the Oldroyd-B constitutive equation. Simulations of deformation for a Newtonian drop in a viscoelastic medium under shear are reported.

scholarly journals A Novel Dynamic Grey Action Quantity GM(1,1,b) Model and Its Application

2019 ◽  
pp. 1-11
Author(s):  
Lang Yu
Keyword(s):  
Prediction Accuracy ◽  
Dynamic Change ◽  
Response Sequence ◽  
Time Response ◽  
Rural Residents ◽  
Time Points ◽  
Numerical Example ◽  
Background Value ◽  
Consumption Index ◽  
Improved Model

The classical GM(1,1) model treats the grey action quantity as an invariant constant, but changes have occurred within the system as time and space change. If the fixed grey action quantity is still used for modeling, the model will have errors. Aiming at this shortcoming, this paper proposes a GM(1,1,b) model in which the grey action quantity can be dynamically changed. Starting from the background value formula, the model solves the grey action quantity at different time points by the development coefficient, and fits the sequence with the DGM(1,1) model, then brings the obtained time response sequence into the classical GM (1, 1) to replaces the grey action quantity constant, so as to establish a GM(1,1,b) model with dynamic change of grey action quantity. Finally, the model is applied to the example of China's rural residents' consumption index. The numerical example shows that the GM(1,1,b) model proposed in this paper effectively improves the prediction accuracy of the model and verifies the effectiveness and practicability of the improved model.

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.

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.

Emulsion processing—from single-drop deformation to design of complex processes and products

2005 ◽  
Vol 60 (8-9) ◽  
pp. 2101-2113 ◽  
Author(s):  
E.J. Windhab ◽  
M. Dressler ◽  
K. Feigl ◽  
P. Fischer ◽  
D. Megias-Alguacil
Keyword(s):  
Drop Deformation ◽  
Single Drop ◽  
Complex Processes ◽  
Emulsion Processing

scholarly journals Bubble Departure Diameter Prediction Uncertainty

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Marko Matkovič ◽  
Boštjan Končar
Keyword(s):  
Prediction Accuracy ◽  
Buoyancy Force ◽  
Lift Force ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Surface Tension Force ◽  
Experimental Accuracy ◽  
Mechanistic Modelling ◽  
Boiling Process ◽  
Heat Partitioning

This paper presents quality assessment of a mechanistic modelling for bubble departure diameter prediction during pool boiling condition. In contrast to flow boiling process only buoyancy force with opposing surface tension force was considered as the responsible mechanisms for bubble departure. Indeed, inertia from the fluid flow around the bubble and the growth force, which describes momentum change due to the evaporation at the bubble base and condensation at the top of the bubble, were all neglected. Besides, shear lift force and quasi-steady drag force as the dominant inertia driven forces were also neglected in the assessment. Rather than trying to model bubble dynamics as precise as possible by properly addressing all the relevant mechanisms available, the work focuses on prediction accuracy of such approach. It has been shown that inlet boundary conditions with realistic experimental accuracy may lead to a significant uncertainty in the prediction of bubble departure diameter, which is intrinsically connected to the uncertainty of most heat partitioning and CHF models.

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.

scholarly journals Kinematic Modelling and Experimental Validation of a Foldable Pneumatic Soft Manipulator

2020 ◽  
Vol 10 (4) ◽  
pp. 1447
Author(s):  
Zhuoqun Liu ◽  
Xiang Zhang ◽  
Hongwei Liu ◽  
Yong Chen ◽  
Yiyong Huang ◽  
...  
Keyword(s):  
Control System ◽  
Prediction Accuracy ◽  
Experimental Validation ◽  
Kinematic Model ◽  
Shape Deformation ◽  
Pneumatic Actuators ◽  
Pneumatic Control ◽  
Directional Movement ◽  
Kinematic Modelling ◽  
Soft Manipulator

A foldable pneumatic soft manipulator, which has the foldability to switch between a contraction state and an expanded state, is proposed in this investigation. The soft manipulator is a structure composed of pneumatic actuators and inflatable straight arms. The directional movement is driven by the pneumatic actuators and the foldability is realized by the inflatable straight arms. Based on this design, the kinematic model of one foldable pneumatic module is developed and presented. The shape deformation and workspace of the pneumatic module is numerically calculated and analyzed. To validate the correctness of the kinematic model, the prototype of one foldable pneumatic module, as well as the relevant pneumatic control system, is designed and developed. The repeatability of the pneumatic module and the model prediction accuracy are tested and validated by the experiment.

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