2-D Modeling of Nonlinear Dynamics of Forcespinning Jet Formation

2021 ◽  
Author(s):  
Dumitru I. Caruntu ◽  
Simon Padron ◽  
Karen Lozano
Keyword(s):  
Fluid Dynamics ◽  
Angular Velocity ◽  
Multiple Scales ◽  
Tangential Velocity ◽  
Production Method ◽  
Orifice Diameter ◽  
Inviscid Fluid ◽  
Exit Angle ◽  
Fluid Level ◽  
Jet Trajectory

Abstract Forcespinning is a novel method that makes use of centrifugal forces to produce nanofibers rapidly and at high yields. To improve and enhance the forcespinning production method, a 2D computational forcespinning inviscid fluid dynamics model is developed. Two models, namely time-independent and time-dependent, are obtained in order to investigate the influence of various parameters on fiber forcespinning formation (trajectory, jet diameter, tangential velocity). The fluid dynamics equations are solved using the method of multiple scales along with the finite difference method, and including slender-jet theory assumptions. It is important to produce jets with small diameters in the micro- and nano-range. The Weber (We) and Rossby (Rb) numbers were found to both expand the jet trajectory as they increased. Increasing We and/or decreasing Rb was found to decrease the jet diameter. Also, by varying forcespinning parameters, it has been found that the jet radius can be decreased by increasing the jet exit angle in the direction of rotation, reducing the spinneret fluid level, increasing the angular velocity of the spinneret, reducing spinneret length, and/or reducing the orifice diameter. Knowing the jet trajectories is important for designing and positioning of fiber collector. It has been found that the trajectories expand out with the increase of the jet exit angle in the direction of rotation, increase of fluid level, increase of angular velocity, and/or increase of the spinneret length. Production rates and jet radii for any predetermined radial collector distance were also determined.

Influence of Viscosity on Forcespinning™ Dynamics

2012 ◽  
Author(s):  
Simon Padron ◽  
Dumitru I. Caruntu ◽  
Karen Lozano
Keyword(s):  
Fluid Dynamics ◽  
Multiple Scales ◽  
Tangential Velocity ◽  
Centrifugal Forces ◽  
Dynamics Model ◽  
Novel Method ◽  
The Finite Difference Method ◽  
Jet Theory ◽  
High Yields ◽  
Fluid Dynamics Equations

Forcespinning™ is a novel method that makes use of centrifugal forces to produce nanofibers rapidly and at high yields. A 2D computational Forcespinning™ viscous fluid dynamics model is developed, that improves on previous models. The fluid dynamics equations are solved using themethod of multiple scales along with the finite difference method, and including slender-jet theory assumptions. The effects that the Reynolds (Re) number has on the resulting fiber trajectory, radius, and tangential velocity are presented.

scholarly journals Determining the Tangential Velocity profile of a Rotating Fluid in a Static Container using Navier–Stokes equations

2020 ◽  
Author(s):  
RAJDEEP TAH ◽  
SARBAJIT MAZUMDAR ◽  
Krishna Kant Parida
Keyword(s):  
Angular Velocity ◽  
Velocity Profile ◽  
Velocity Gradient ◽  
Stokes Equations ◽  
Tangential Velocity ◽  
Navier Stokes ◽  
Rotating Fluid ◽  
Navier Stokes Equations ◽  
Similar Principle ◽  
Tangential Velocity Profile

The shape of the liquid surface for a fluid present in a uniformly rotating cylinder is generally determined by making a Tangential velocity gradient along the radius of the rotating cylindrical container. A very similar principle can be applied if the direction of the produced velocity gradient is reversed, for which the source of rotation will be present at the central axis of the cylindrical vessel in which the liquid is present. Now if the described system is completely closed, the angular velocity will decrease as a function of time. But when the surface of the rotating fluid is kept free, then the Tangential velocity profile would be similar to that of the Taylor-Couette Flow, with a modification that; due to formation of a curvature at the surface, the Navier-Stokes law is to be modified. Now the final equation may not seem to have a proper general solution, but can be approximated to certain solvable expressions for specific cases of angular velocity.

On the computation of measure-valued solutions

Acta Numerica ◽  
2016 ◽  
Vol 25 ◽  
pp. 567-679 ◽  
Author(s):  
Ulrik S. Fjordholm ◽  
Siddhartha Mishra ◽  
Eitan Tadmor
Keyword(s):  
Fluid Dynamics ◽  
Materials Science ◽  
Numerical Algorithms ◽  
Approximate Solutions ◽  
Variational Problems ◽  
Convincing Evidence ◽  
Young Measures ◽  
Inviscid Fluid ◽  
New Paradigm ◽  
Uniqueness Of Solutions

A standard paradigm for the existence of solutions in fluid dynamics is based on the construction of sequences of approximate solutions or approximate minimizers. This approach faces serious obstacles, most notably in multi-dimensional problems, where the persistence of oscillations at ever finer scales prevents compactness. Indeed, these oscillations are an indication, consistent with recent theoretical results, of the possible lack of existence/uniqueness of solutions within the standard framework of integrable functions. It is in this context that Young measures – parametrized probability measures which can describe the limits of such oscillatory sequences – offer the more general paradigm of measure-valued solutions for these problems.We present viable numerical algorithms to compute approximate measure-valued solutions, based on the realization of approximate measures as laws of Monte Carlo sampled random fields. We prove convergence of these algorithms to measure-valued solutions for the equations of compressible and incompressible inviscid fluid dynamics, and present a large number of numerical experiments which provide convincing evidence for the viability of the new paradigm. We also discuss the use of these algorithms, and their extensions, in uncertainty quantification and contexts other than fluid dynamics, such as non-convex variational problems in materials science.

scholarly journals Numerical Simulations of Two-Layer Flow past Topography. Part I: The Leeside Hydraulic Jump

2018 ◽  
Vol 75 (4) ◽  
pp. 1231-1241 ◽  
Author(s):  
Richard Rotunno ◽  
George H. Bryan
Keyword(s):  
Fluid Dynamics ◽  
Hydraulic Jump ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Fluid Layer ◽  
Transition To Turbulence ◽  
Height Velocity ◽  
Inviscid Fluid ◽  
Initial Value ◽  
Density Interface

Abstract Laboratory observations of the leeside hydraulic jump indicate it consists of a statistically stationary turbulent motion in an overturning wave. From the point of view of the shallow-water equations (SWE), the hydraulic jump is a discontinuity in fluid-layer depth and velocity at which kinetic energy is dissipated. To provide a deeper understanding of the leeside hydraulic jump, three-dimensional numerical solutions of the Navier–Stokes equations (NSE) are carried out alongside SWE solutions for nearly identical physical initial-value problems. Starting from a constant-height layer flowing over a two-dimensional obstacle at constant speed, it is demonstrated that the SWE solutions form a leeside discontinuity owing to the collision of upstream-moving characteristic curves launched from the obstacle. Consistent with the SWE solution, the NSE solution indicates the leeside hydraulic jump begins as a steepening of the initially horizontal density interface. Subsequently, the NSE solution indicates overturning of the density interface and a transition to turbulence. Analysis of the initial-value problem in these solutions shows that the tendency to form either the leeside height–velocity discontinuity in the SWE or the overturning density interface in the exact NSE is a feature of the inviscid, nonturbulent fluid dynamics. Dissipative turbulent processes associated with the leeside hydraulic jump are a consequence of the inviscid fluid dynamics that initiate and maintain the locally unstable conditions.

scholarly journals From the world of wearable grasses: Vetiver (The use of local place-based knowledge to develop a scalable circular economy that enables positive social impact within the textile industry)

2021 ◽  
Author(s):  
◽  
Ananya Khare
Keyword(s):  
Textile Industry ◽  
Social Impact ◽  
Multiple Scales ◽  
Driving Forces ◽  
Modern Society ◽  
Wicked Problems ◽  
Production Method ◽  
Raw Material ◽  
Wicked Problem ◽  
Fast Fashion

<p>Progress is the first instinct for humans, with innovation and problem-solving driving forces within every generation. Sadly, as a part of this process, there has been a lack of recognition or interest in age-old, indigenous, local or place-based knowledge. In contrast to this belief of globalisation, this thesis advocates Indigenous Wisdom as a bridge to solving ‘wicked problems’ of our modern society. Horst Rittel describes wicked problems as interconnected and networked by nature, existing on multiple scales. This research identifies one such a wicked problem of textile pollution. One of the factors contributing to textile pollution is the resulting landfill. Connected to, contributing to or more abruptly put, causing this problem is fast fashion. In 2011 the United Nation Environment Program estimated that without intervention, the rate of consumption for fast fashion would continue to grow up to three-fold by the year 2050. The research explores the need for a durable, economical and more sustainable textile option that can both minimise production waste and is affordable for consumers. Paralleling Transition Design with local placed -based knowledge this research identifies a raw material that is the vetiver grass, a sustainable and straightforward production method, a community that is the inmates of Bhopal Central Jail, and a scalable circular economic model and connect them to make fabric based items for their use or sale and trade beyond their community.</p>

scholarly journals DESAIN NOSEL ROKET CAIR RCX250 MENGGUNAKAN METODE PARABOLIK DENGAN MODIFIKASI SUDUT EKSPANSI

2012 ◽  
Vol 9 (1) ◽  
Author(s):  
Eko Priamadi ◽  
Arif Nur Hakim ◽  
Romie O. Bura
Keyword(s):  
Fluid Dynamics ◽  
Design Method ◽  
Exit Angle ◽  
Nozzle Design ◽  
Conical Nozzle ◽  
Initial Angle ◽  
Simulation Results ◽  
Nozzle Thrust ◽  
Dynamics Method ◽  
Maximum Thrust

 The present research is conducted to design the optimum nozzles for RCX250 engine, that is designed to produce maximum thrust of 250 kgf with combination of LOX and Kerosene as its propellant. The new nozzles were determined to be parabolic nozzle, with conical nozzle as its comparison. The parabolic nozzle was designed using Thrust Optimized Parabolic (TOP) method invented by G.V.R.Rao. TOP nozzle design method is performed by approximating a Thrust Optimized Contoured (TOC) Nozzle using parabolic equation. The method would result more efficient nozzle than conical or ideal bell nozzle. Further, the parabolic nozzle were modified in its initial and exit angle to create uniform velocities distribution at nozzle exit. A Computational Fluid Dynamics Method (CFD) is used to simulate the nozzle designs. The simulation was carried out in axis-symmetric condition using commercial CFD software. The simulation results show that MOD 1 nozzle, with initial angle (θN) 26 deg and exit angle (θe) 12 deg, gives maximum thrust, which is 4.67 % higher than reference conical nozzle. Key words:Liquid rocket, Parabolic nozzle, Thrust, CFD

Theoretical Investigation on the Characteristics of Leak Noise for Natural Gas Pipelines

2020 ◽  
Vol 28 (03) ◽  
pp. 2050005
Author(s):  
Zewei Zhang ◽  
Hongyong Yuan ◽  
Ming Fu ◽  
Tao Chen ◽  
Yan Gao ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Natural Gas ◽  
Dynamic Pressure ◽  
Spectral Characteristics ◽  
Orifice Diameter ◽  
Dipole Source ◽  
Gas Pipelines ◽  
Buried Pipelines ◽  
Spectral Parameters ◽  
Natural Gas Pipelines

This paper is concerned with the spectral characteristics of leak noise at the source relevant to fluid dynamics for natural gas pipelines. Comparison is made between the flow field characteristics for the buried and above-ground pipelines to demonstrate the differences in aero-acoustics generation mechanism. The fundamental spectral parameters including the sound pressure level (SPL) and power spectral density (PSD), are extracted to characterize the leak noise under different pipeline conditions of operation pressure and leak orifice diameter. Numerical results show that the leak noise of buried pipelines has less energy and are more concentrated at lower frequencies, compared with that of above-ground pipelines. It is demonstrated that leak noise is predominantly governed by the dipole and the quadrupole sources, generated from the gas–solid interaction and turbulent disturbance, respectively. It is shown that the dipole source is attenuated and the quadrupole source is amplified with the leak orifice diameter for buried pipelines whereas both are amplified for above-ground pipelines. Moreover, it is suggested that the feature parameters of fluid dynamics, such as the average dynamic pressure and turbulent kinetic energy, can be used to characterize the leak noise mechanism for natural gas pipelines.

A semianalytical method for studying the performances of aerostatic thrust bearing

2018 ◽  
Vol 233 (4) ◽  
pp. 628-637
Author(s):  
Jianbo Zhang ◽  
Chunxiao Jiao ◽  
Donglin Zou ◽  
Na Ta ◽  
Zhushi Rao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Thrust Bearing ◽  
Separation Of Variables ◽  
Orifice Diameter ◽  
Thrust Bearings ◽  
Supply Pressure ◽  
Semianalytical Method

The solution of Reynolds equation and computational fluid dynamics are widely employed for the lubrication performance analysis of aerostatic thrust bearing. However, the solution of Reynolds equation may be inaccurate and cannot present detailed performance near orifice, while computational fluid dynamics method has low computational efficiency with time consumption in mesh generation and solving Navier–Stokes equations. In order to overcome the drawbacks of Reynolds equation and computational fluid dynamics, based on the method of separation of variables, a semianalytical method is developed for describing the characteristics of aerostatic bearings available. The method of separation of variables considering the initial and viscous effect is more accurate than the Reynolds equation and can present detailed performance near orifice in the aerostatic thrust bearings, while method of separation of variables has great computational efficiency compared to computational fluid dynamics. Meanwhile, the pressure distribution calculated by method of separation of variables is compared to the published experimental data and the results obtained by computational fluid dynamics. The comparative results indicate validity of the method. Furthermore, the influences of flow and geometry parameters, such as supply pressure, orifice diameter, film thickness, and bearing radius, on the characteristics of aerostatic thrust bearings with single orifice are studied. The results show that there exists pressure depression phenomenon near orifice. The depression phenomenon is strengthened with increase of film thickness and supply pressure and decrease of orifice diameter and bearing radius, while the maximum speed increases with strengthening of pressure depression due to decrease of minimum local pressure near orifice. Moreover, the bearing capacity increases with increase of supply pressure, orifice diameter, and bearing radius and decreases with increase of film thickness, while mass flow rate increases with supply pressure, orifice diameter, and film thickness and it is not sensitive to bearing radius.

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