Negative Squeeze Research Articles

Heat and Mass Transfer Analysis of an unsteady Non-Newtonian Magnetohydrodynamic Fluid Flow (Semi-Analytical Solution)

In the presence of a time-dependent chemical reaction, this work investigates unsteady squeezing Casson nanofluid flow and heat transfer between two parallel plates under the influence of a uniform magnetic field. Considering the effects of viscosity dissipation, heat generation from friction resulting from flow shear, Brownian motion, Joule heating, and thermodiffusion. The problem's nonlinear differential equations are solved using the Runge–Kutta (RK-4) technique and the Homotopy Perturbation technique. The excellent accuracy of the results is evident since they have been compared with other results from earlier research. In the form of graphs and tables, flow behavior under the many physical factors that are modified is also covered and well described. This work has shown that, by normalizing flow behavior, magnetic fields may be utilized to manage a variety of flows. Additionally, it is demonstrated that in every situation, the effects of positive and negative squeeze numbers on heat and mass transfer flow are opposite. Moreover, the thermophoresis parameter decreases as the concentration field increases. However, when the Brownian motion parameter is increased, the concentration profile gets better. Additionally, several other significant factors were examined. The results of this study can facilitate quicker and easier research and assist engineers.

Fractional analysis of unsteady squeezing flow of Casson fluid via homotopy perturbation method

The objective of this article is to model and analyze unsteady squeezing flow of fractional MHD Casson fluid through a porous channel. Casson fluid model is significant in understanding the properties of non-Newtonian fluids such as blood flows, printing inks, sauces and toothpaste etc. This study provides important results as unsteady flow of Casson fluid in fractional sense with aforementioned effects has not been captured in existing literature. After applying similarity transformations along with fractional calculus a highly non-linear fractional-order differential equation is obtained. Modeled equation is then solved along with no-slip boundary conditions through a hybrid of Laplace transform with homotopy perturbation algorithm. For validity purposes, solution and errors at various values in fractional domain are compared with existing results. LHPM results are better in terms of accuracy than other available results in literature. Effects of fractional parameter on the velocity profile, skin friction and behaviors of involved fluid parameters is the focal point of this study. Comprehensive, quantitative and graphical analysis is performed for investigating the effects of pertinent fluid parameters on the velocity profile and skin friction. Analysis revealed that fractional parameter depicts similar effect in case of positive and negative squeeze number. Also, skin friction decreases with an increasing fractional parameter. Moreover, in fractional environment Casson parameter has shown similar effect on the velocity profile in case of positive and negative squeeze number.

Electroosmotic modulated unsteady squeezing flow with temperature-dependent thermal conductivity, electric and magnetic field effects

Modern lubrication systems are increasingly deploying smart (functional) materials. These respond to various external stimuli including electrical and magnetic fields, acoustics, light etc. Motivated by such developments, in the present article unsteady electro-magnetohydrodynamics squeezing flow and heat transfer in a smart ionic viscous fluid intercalated between parallel plates with zeta potential effects is examined. The proposed mathematical model of problem is formulated as a system of partial differential equations (continuity, momenta and energy). Viscous dissipation and variable thermal conductivity effects are included. Axial electrical distribution is also addressed. The governing equations are converted into ordinary differential equations via similarity transformations and then solved numerically with MATLAB software. The transport phenomena are scrutinized for both when the plates move apart or when they approach each other. Also, the impact of different parameters such squeezing number, variable thermal conductivity parameter, Prandtl number, Hartmann number, Eckert number, zeta potential parameter, electric field parameter and electroosmosis parameter on the axial velocity and fluid temperature are analysed. For varied intensities of applied plate motion, the electro-viscous effects derived from electric double-capacity flow field distortions are thoroughly studied. It has been shown that the results from the current model differ significantly from those achieved by using a standard Poisson–Boltzmann equation model. Axial velocity acceleration is induced with negative squeeze number (plates approaching, S < 0) in comparison to that of positive squeeze number (plates separating, S > 0). Velocity enhances with increasing electroosmosis parameter and zeta potential parameter. With rising values of zeta potential and electroosmosis parameter, there is a decrease in temperatures for U e > 0 for both approaching i.e. squeezing plates (S < 0) and separating (S > 0) cases. The simulations provide novel insights into smart squeezing lubrication with thermal effects and also a solid benchmark for further computational fluid dynamics investigations.

Modeling and study of the arterial blood flow loaded with nanoparticles under squeezing action in presence of a magnetic field

This article is intended to study the arterial blood flow with nanoparticles in a magnetic field due to the squeezing action of the heart, the study was treated as acasson nanofluid flowing between two parallel plates placed at a distance varying in time and under the influence of a uniform magnetic field with variable chemical reaction. Considering the following effects: viscous dissipation, generation of heat due to friction caused by shear in the flow, joule heating, brownian motion, and the influence of thermo-diffusion. Homotopy Perturbation Method is used to solve the nonlinear differential equations governing the problem. To verify the accuracy of the analytical method used, the results of the homotopy perturbation method (HPM) are compared with the results of the Numerical method using the fourth-order Runge–Kutta method (RK-4) and other results obtained in previous works so that the high accuracy of results is clear. Flow behaviour under the modifying involved physical parameters is also discussed and explained in detail in the form of graphs and tables. Through this study it is observed that magnetic field can be used as a control phenomenon in many flows as it normalizes the flow behaviour. Also, it is shown that positive and negative squeeze numbers have opposite effects on heat and mass transfer flow throughout all the cases. Further, the concentration field is a decreasing function of thermophoresis parameter. While, concentration profile enhances with raising brownian motion parameter. And various other important parameters were analyzed. Findings from this study can help engineers to improve and researchers to investigate faster and easier.

Kavitationsdynamik in geschmierten Kontakten - Weiterentwicklung eines Modells mit Blasendynamik

Cavitation is a widespread phenomenon in journal bearings and other lubricated contacts. In lubricated contacts, tensile stresses can occur in the lubricant as a result of cavitation dynamics. These tensile stresses, hardly known with respect to duration and magnitude, are investigated with a simulation model consisting of Reynolds equation and Rayleigh-Plesset equation for the negative squeeze motion of circular plate and spherical cap. The tensile stresses are practically relevant in calculating the opening times of valves (oil stiction). It may assumed that the short-time tensile stresses occurring in the simulation model also occur in other cases and have an influence on material fatigue and wear of the components involved and are thus practically relevant.

BUBBLE DYNAMICS-BASED MODELING OF THE CAVITATION DYNAMICS IN LUBRICATED CONTACTS

Cavitation is a common phenomenon in fluid machinery and lubricated contacts. In lubricated contacts, there is a presumption that the short-term tensile stresses at the onset of bubble formation have an influence on material wear. To investigate the duration and magnitude of tensile stresses in lubricating films using numerical simulation, a suitable simulation model must be developed. The chosen simulation approach with bubble dynamics is based on the coupling of the Reynolds equation and Rayleigh-Plesset equation (introduced about 20 years ago by Someya).Following the basic approach from the author’s earlier papers on the negative squeeze motion with bubble dynamics for the simulation of mixed lubrication of rough surfaces, the paper at hand shows modifications to the Rayleigh-Plesset equation that are required to get the time scale for the dynamic processes right. This additional term is called the dilatational viscosity term, and it significantly influences the behavior of the numerical model.

Leg Injury - Football

HISTORY: A 12-year old male quarterback sustained a right leg injury while cutting back across the field. He was running across the field and made a lateral cut to change directions, as this happened he tripped over himself and fell without a twisting motion. He landed on his right lateral leg with immediate pain to the fibular head. There was no numbness, tingling, weakness or radiation of pain however he had a noticeable limp. He presented to clinic 2 days later and denied any prior injuries or trauma to the area. PHYSICAL EXAMINATION:2 days post injury (PCP office) — No deformity, normal knee and ankle exams, no bony tenderness, moderate postero-lateral edema of proximal right lower leg, painful/antalgic gait, TTP lateral gastrocnemius and soleus, negative Thompson's.4 days post injury (Sports Medicine Clinic) — Consistent with prior exam, new findings: point TTP just distal to fibular head, decreased edema, negative squeeze test, negative ER test. DIFFERENTIAL DIAGNOSIS: 1. R fibular contusion 2. R knee apophysitis 3. LCL sprain 4. Gastrocnemius contusion/strain 5. Distal Bicep Femoris strain TEST AND RESULTS: XR: R Tib/Fib AP and Lateral radiographs 2 days after injury — Bones/joints/soft tissue appear unremarkable. Repeat XR 13 days post injury — subtle irregularity along the lateral aspect of the proximal fibula physis with associated periostitis. Final XR 20 days post injury — Noted irregularity along the lateral aspect of the proximal fibula physis with increased benign periostitis. FINAL WORKING DIAGNOSIS: Salter-Harris II fracture of R proximal fibula physis TREATMENT AND OUTCOMES: 1. Cam walker boot 3 weeks with weekly exams/XRs 2. 20 days out from injury completely normal RLE exam, no pain, full ROM, XRs suggestive for healing SH2 fracture; patient was able to return to football as tolerated. DISCUSSION: In isolation this is a very rare injury. There was one reported case of a SH-3 fracture that presented with initial knee injury and ROM deficits that was treated non-operatively. Most injuries to the proximal physis of the fibula occur in combination with an interosseous membrane/syndesmotic and distal tibiofibular injury - must rule out a Maisonneuve injury. The presenting complaint was pain and edema in the region of the soleus this may have been a soleus traction injury to the apophysis vs direct trauma from the fall.

Review on the Bubble Dynamics Based Cavitation Dynamics for the Negative Squeeze Motion in Lubricated Contacts

Simulation models for the cavitation dynamics in lubricated contacts can be roughly clustered into two groups: either without or with bubble dynamics, the first one being the standard case for most fluid film bearing calculations. The approach with bubble dynamics has been introduced to the lubrication community about 20 years ago by Someya, and it is based on the coupling of Reynolds equation and Rayleigh-Plesset equation. It has been used for journal bearings, squeeze film dampers, and it is essentially required for correct numerical calculations of the negative squeeze motion (i. e. the separation of two plates) or the oil stiction problem. More than a decade ago, in 2009, the first paper on the negative squeeze motion with bubble dynamics -- allowing numerical calculations of tensile stresses in the lubricant -- had been published. The application in mind is the simulation of mixed lubrication for rough surfaces. The negative squeeze motion is then understood as the motion of asperities (on smaller length scales). The paper at hand summarizes some of the research on the dynamics of cavitation in lubricated contacts from different research groups from the last 10 to 15 years and sketches key topics for further research on the topic. The roadmap is centered around the three key issues that remained from the previous research of the author: (a) numerical stability of the calculations for curved plates, (b) characteristic time scale for separation of plates and (c) experimental evidence for validating the calculation results.

Slip Analysis at Fluid-Solid Interface in MHD Squeezing Flow of Casson Fluid through Porous Medium

An unsteady squeezing flow of Casson fluid having Magneto Hydro Dynamic effect and passing through porous medium channel with slip at the boundaries has been modelled and analyzed. Similarity transformations are applied to the governing partial differential equations of the Casson model to get a highly non-linear fourth order ordinary differential equation. The obtained equation is then solved analytically using the Homotopy Perturbation Method (HPM) for uniform and non-uniform slip at the boundaries. Five cases of boundary conditions, representing slip at upper wall only, uniform slip at both walls, non-uniform slip where slip at upper wall is greater than that of lower wall, non-uniform slip where slip at lower wall is greater than that of upper wall, and slip at lower wall only are considered and thoroughly investigated. Validation is performed by solving the equation numerically using fourth order explicit Runge Kutta method (ERK4). Both analytical and numerical results show good agreement. Lastly, the effects of various fluid parameters on the velocity profile are investigated for each case graphically. Analysis of these plots show that the positive and negative squeeze numbers have opposite effect on the velocity profile throughout all the cases. It is also observed that various fluid parameters like Casson, MHD, and Permeability have similar effects on the velocity profile in the cases when slip is occurring at the upper wall only, and non-uniform slip at both the boundaries with slip at lower wall is greater than upper wall. Furthermore, similar effects have been observed when slip is uniform at both the boundaries, and in case of non-uniform slip with slip at lower wall is less than the upper wall.

Unsteady Squeezing Flow of Casson Fluid with Magnetohydrodynamic Effect and Passing through Porous Medium

An unsteady squeezing flow of Casson fluid having magnetohydrodynamic (MHD) effect and passing through porous medium channel is modeled and investigated. Similarity transformations are used to convert the partial differential equations (PDEs) of non-Newtonian fluid to a highly nonlinear fourth-order ordinary differential equation (ODE). The obtained boundary value problem is solved analytically by Homotopy Perturbation Method (HPM) and numerically by explicit Runge-Kutta method of order 4. For validity purpose, we compare the analytical and numerical results which show excellent agreement. Furthermore, comprehensive graphical analysis has been made to investigate the effects of various fluid parameters on the velocity profile. Analysis shows that positive and negative squeeze numberSqhave opposite effect on the velocity profile. It is also observed that Casson parameterβshows opposite effect on the velocity profile in case of positive and negative squeeze numberSq. MHD parameterMgand permeability constantMphave similar effects on the velocity profile in case of positive and negative squeeze numbers. It is also seen that, in case of positive squeeze number, similar velocity profiles have been obtained forβ,Mg, andMp. Besides this, analysis of skin friction coefficient has also been presented. It is observed that squeeze number, MHD parameter, and permeability parameter have direct relationship while Casson parameter has inverse relationship with skin friction coefficient.

The diagnostic accuracy of the squeeze test to identify arthritis: a cross-sectional cohort study

ObjectivesIn daily practice, the squeeze test is used to screen for arthritis in metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints. This cross-sectional cohort study determined the diagnostic accuracy of this test.MethodsPatients...

A 17-Year-Old Ballet Dancer with Medial Ankle Pain

A 17-Year-Old Ballet Dancer with Medial Ankle Pain

A Bubble Dynamics Based Approach to the Simulation of Cavitation in Lubricated Contacts

The negative squeeze lubrication problem is investigated by means of numerical simulations that account for the dynamics of vaporization. The model is based on bubble dynamics, governed by the Rayleigh–Plesset equation, and the Reynolds equation for compressible fluids. Unlike most existing simulation models our model can predict tensile stresses in the fluid film prior to its rupture, which is in accordance with experimental evidence.

Mushy Regions in Negative Squeeze Films

An elegant experiment described by Hayes and Feiten in 1964 suggests a novel free boundary model for the evolution of a mushy region in a negative squeeze film. The mushy region nucleates when the plates enclosing the film are pulled apart sufficiently rapidly for the pressure to drop to a critical value at some point of the film. On the basis of an earlier one-dimensional analysis, a complementarity model is proposed for quite general mush evolutions and a regularization of this model is studied analytically and numerically.

Finite Element Mass-Conserving Cavitation Algorithm in Pure Squeeze Motion. Validation/Application to a Connecting- Rod Small End Bearing

A simple analytical approach using conditions of conservation of the mass is proposed for the 1-D “negative squeeze” lubrication problem in order to calculate the cavitation boundary position during oscillatory motion of two plates. The same geometrical case is analyzed using Bonneau’s finite element code. Good agreements between analytical and numerical results support validation of Bonneau’s algorithm. As an example of application of this algorithm to squeeze motion case, the EHD lubrication of an elastic connecting-rod small end bearing is analyzed. Influences of the shaft elasticity and lubricant piezoviscosity are presented. [S0742-4787(00)02101-9]

Cavitation in Normal Separation of Square and Circular Plates

The “negative squeeze” lubrication problem is investigated by means of a mass-conservating finite element cavitation algorithm (described elsewhere) within the context of a dimensionless study of lubricant film behavior between rigid, parallel separating surfaces. Appropriate mesh geometries which capture spatial and temporal mixture density history and satisfy JFO conditions on the cavitation interface are determined. Present simulation results agree qualitatively with previous experiments, supporting the validity of the algorithm and its utility in the bearing design process.

Nonlinear Finger Growth Analysis of Viscous Fluid between Circular Parallel Plates by the Boundary Element Method.

In the present paper, the authors develop a time-dependent numerical algorithm using the boundary element method to simulate the behavior of the free surface of a thin liquid film between two parallel circular plates in negative squeeze motion. A nonlinear evolution of fingers on the free surface is numerically simulated in order to examine the validity of the criterion for meniscus instability on the basis of the linear instability theory and to confirm the validity of the formulation in the boundary element method. Several types of disturbances were imposed at the free surface as an initial perturbation in the simulation. Consequently, when the disturbances with the wavelength distributed at random around the most unstable wavelength given by our theory were applied, finger patterns similar to those formed in the experiment were formed in the simulation.

The Meniscus Instability in Non-Newtonian Negative Squeeze Films

This paper treats an instability at the free surface of non-Newtonian (power-law) fluid films between two tilted plates in a negative squeeze motion. The meniscus instability in a fluid with the power-law constitutive equation was analyzed on the basis of the linear stability theory. In the analysis, a capillary number for the power-law fluid was newly defined and the relationship between the capillary number and the criterion for the instability of meniscus was theoretically deduced. In the experiment, a water solution of polyacrylamide (separan) whose viscosity obeys a power-law of the strain rate was used as a sample fluid, the meniscus instability in the fluid was examined by using a VTR and the wavelength of disturbances was measured. The theoretical criterion for the instability was in good agreement with experiments and the capillary number could rearrange well the experimental results for the disturbances.

A meniscus instability for the separation of a thin liquid film between parallel circular plates. 1st report. Experiment on growth of disturbances.

In this paper, the behavior of the meniscus between two circular parallel plates in negative squeeze motion is theoretically and experimentally investigated. According to the previous study on two tilted rectangular plates, a local capillary number for circular liquid film is newly introduced and the theoretical relation between the local capillary number and the nondimensional wave number of disturbance agrees well the experimental one. It is however found that the nondimensional wave number of the experiments deviates from the theory in the case of high viscous liquid. The growth process of disturbances into fingers is precisely investigated by measuring the tip curvature of the fingers. The simple relationship between the ratio of the curvature to the thickness of the liquid and that of the curvature to the position of the tip can be found experimentally.