Interfacial Forces and Momentum Exchange Closure

2015 ◽  
pp. 159-191 ◽  
Author(s):  
Christophe Morel
Keyword(s):  
Momentum Exchange ◽  
Interfacial Forces

Systematization of Shock Response Control Based on Momentum Exchange and Energy Exchange and Its Application to Lunar/Planetary Spacecraft

Impact ◽  
2019 ◽  
Vol 2019 (10) ◽  
pp. 73-75
Author(s):  
Susumu Hara
Keyword(s):  
Energy Exchange ◽  
Control Mechanism ◽  
Cost Effective ◽  
Aerospace Engineering ◽  
Single Test ◽  
Momentum Exchange ◽  
Mars Rover ◽  
Response Control ◽  
Shock Control ◽  
Shock Response

Professor Susumu Hara is based at the Department of Aerospace Engineering, Nagoya University in Japan explains that when the Mars rover Opportunity was set to land on that planet in the first weeks of 2004, onlookers held their breath as it dropped from orbit and hurtled toward the red surface. 'Any failure in the calculations or landing systems would mean a harder than expected impact,' he highlights. 'The impacts sustained by a rover such as Opportunity can derail a mission before it even starts, damaging cargo or vital systems required to complete the mission.' Impacts occur during landing but also as the craft enters the atmosphere, when it makes sudden moves, while it is on surface or when debris strikes it. 'Therefore, a system and materials to protect a craft are vital,' outlines Hara. 'Surprisingly, the solutions to this problem are not sophisticated. In fact, most craft still employ devices resembling automobile bumpers, which absorb the energy from an impact by crumpling under the force of said impact.' Unfortunately, these cannot be reused, even during testing phases a new prototype is required after every single test run. Recent missions also employed techniques like airbags or sky cranes. While successful they too have drawbacks. 'Airbags create huge rebounds which can jostle the craft and the contents inside while sky cranes are extremely costly to develop,' Hara says. For this reason, he is dedicated to designing a new highly reliable and cost-effective shock control mechanism.

INFLUENCE OF SEA SPRAY AND RAINDROP ON THE MOMENTUM EXCHANGE AT AIR-SEA INTERFACE

2018 ◽  
Vol 74 (4) ◽  
pp. I_265-I_270 ◽  
Author(s):  
Hiroki OKACHI ◽  
Tomohito J. YAMADA ◽  
Yasunori WATANABE
Keyword(s):  
Sea Spray ◽  
Momentum Exchange

Substructural identification with weighted global iteration considering unknown interfacial forces and external excitation

Measurement ◽  
2021 ◽  
pp. 109537
Author(s):  
Jia He ◽  
Mengchen Qi ◽  
Xugang Hua ◽  
Zhengqing Chen ◽  
Ou Yang ◽  
...  
Keyword(s):  
External Excitation ◽  
Interfacial Forces ◽  
Global Iteration

scholarly journals Superfluid vortex-mediated mutual friction in non-homogeneous neutron star interiors

2020 ◽  
Vol 499 (3) ◽  
pp. 3690-3705
Author(s):  
M Antonelli ◽  
B Haskell
Keyword(s):  
Neutron Star ◽  
Normal Component ◽  
Homogeneous Medium ◽  
Outer Core ◽  
Two Dimensions ◽  
Pinning Force ◽  
Mutual Friction ◽  
Momentum Exchange ◽  
Drag Forces ◽  
Vortex Lines

ABSTRACT Understanding the average motion of a multitude of superfluid vortices in the interior of a neutron star is a key ingredient for most theories of pulsar glitches. In this paper, we propose a kinetic approach to compute the mutual friction force that is responsible for the momentum exchange between the normal and superfluid components in a neutron star, where the mutual friction is extracted from a suitable average over the motion of many vortex lines. As a first step towards a better modelling of the repinning and depinning processes of many vortex lines in a neutron star, we consider here only straight and non-interacting vortices: we adopt a minimal model for the dynamics of an ensemble of point vortices in two dimensions immersed in a non-homogeneous medium that acts as a pinning landscape. Since the degree of disorder in the inner crust or outer core of a neutron star is unknown, we compare the two possible scenarios of periodic and disordered pinscapes. This approach allows us to extract the mutual friction between the superfluid and the normal component in the star when, in addition to the usual Magnus and drag forces acting on vortex lines, also a pinning force is at work. The effect of disorder on the depinning transition is also discussed.

Momentum exchange impact damper design methodology for object-wall-collision problems

2017 ◽  
Vol 24 (14) ◽  
pp. 3206-3218
Author(s):  
Yohei Kushida ◽  
Hiroaki Umehara ◽  
Susumu Hara ◽  
Keisuke Yamada
Keyword(s):  
Optimal Design ◽  
Design Methodology ◽  
Design Parameters ◽  
Momentum Exchange ◽  
Impact Damper ◽  
One Dimensional ◽  
Practical Design ◽  
Wall Collision ◽  
Damper Design ◽  
And Control

Momentum exchange impact dampers (MEIDs) were proposed to control the shock responses of mechanical structures. They were applied to reduce floor shock vibrations and control lunar/planetary exploration spacecraft landings. MEIDs are required to control an object’s velocity and displacement, especially for applications involving spacecraft landing. Previous studies verified numerous MEID performances through various types of simulations and experiments. However, previous studies discussing the optimal design methodology for MEIDs are limited. This study explicitly derived the optimal design parameters of MEIDs, which control the controlled object’s displacement and velocity to zero in one-dimensional motion. In addition, the study derived sub-optimal design parameters to control the controlled object’s velocity within a reasonable approximation to derive a practical design methodology for MEIDs. The derived sub-optimal design methodology could also be applied to MEIDs in two-dimensional motion. Furthermore, simulations conducted in the study verified the performances of MEIDs with optimal/sub-optimal design parameters.

A Model Constraint for Polydisperse Solids in Multifluid Flows

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Michael P. Kinzel ◽  
Leonard Joel Peltier ◽  
Brigette Rosendall ◽  
Mallory Elbert ◽  
Andri Rizhakov ◽  
...  
Keyword(s):  
Model Development ◽  
Fluid Flows ◽  
Momentum Exchange ◽  
Carrier Fluid ◽  
Single Carrier ◽  
Cfd Models ◽  
Model Constraint ◽  
Level Model ◽  
Consistency Constraint ◽  
Multiphase Fluid

A method to assess computational fluid dynamics (CFD) models for polydisperse granular solids in a multifluid flow is developed. The proposed method evaluates a consistency constraint, or a condition that an Eulerian multiphase solution for a monodisperse material in a single carrier fluid is invariant to an arbitrary decomposition into a pseudo-polydisperse mixture of multiple, identical fluid phases. The intent of this condition is to develop tests to assist model development and testing for multiphase fluid flows. When applied to two common momentum exchange models, the constraint highlights model failures for polydisperse solids interacting with a multifluid flow. It is found that when inconsistency occurs at the algebraic level, model failure clearly extends to application. When the models are reformulated to satisfy the consistency constraint, simple tests and application-scale simulations no longer display consistency failure.

scholarly journals On the Nature of Near-Inertial Oscillations in the Uppermost Part of the Ocean and a Possible Route toward HF Radar Probing of Stratification

2015 ◽  
Vol 45 (10) ◽  
pp. 2660-2678 ◽  
Author(s):  
Victor I. Shrira ◽  
Philippe Forget
Keyword(s):  
Mixed Layer ◽  
Vertical Mixing ◽  
Hf Radar ◽  
Momentum Exchange ◽  
Inertial Oscillations ◽  
Weak Density ◽  
Gulf Of Lion ◽  
Vertical Heat ◽  
Northwestern Mediterranean ◽  
Vertical Localization

AbstractInertial band response of the upper ocean to changing wind is studied both theoretically and by analysis of observations in the northwestern Mediterranean. On the nontraditional f plane, because of the horizontal component of the earth’s rotation for waves of inertial band with frequencies slightly below the local inertial frequency f, there is a waveguide in the mixed layer confined from below by the pycnocline. It is argued that when the stratification is shallow these waves are most easily and strongly excited by varying winds as near-inertial oscillations (NIOs). These motions have been overlooked in previous studies because they are absent under the traditional approximation. The observations that employed buoys with thermistors, ADCPs, and two 16.3-MHz Wellen Radar (WERA) HF radars were carried out in the Gulf of Lion in April–June 2006. The observations support the theoretical picture: a pronounced inertial band response occurs only in the presence of shallow stratification and is confined to the mixed layer, and the NIO penetration below the stratified layer is weak. NIO surface magnitude and vertical localization are strongly affected by the presence of even weak density stratification in the upper 10 m. The NIO surface signatures are easily captured by HF radars. Continuous 1.8-yr HF observations near the Porquerolles Island confirm that shallow stratification is indeed the precondition for a strong NIO response. The response sensitivity to stratification provides a foundation for developing HF radar probing of stratification and, indirectly, vertical mixing, including spotting dramatic mixing events and spikes of vertical heat, mass, and momentum exchange.

scholarly journals Sensitivity of Hurricane Intensity Forecast to Convective Momentum Transport Parameterization

2006 ◽  
Vol 134 (2) ◽  
pp. 664-674 ◽  
Author(s):  
Jongil Han ◽  
Hua-Lu Pan
Keyword(s):  
Wind Shear ◽  
Vertical Wind Shear ◽  
Momentum Transport ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Momentum Exchange ◽  
Forecast System ◽  
Hurricane Intensity ◽  
Convective Momentum Transport ◽  
The Many

Abstract A parameterization of the convection-induced pressure gradient force (PGF) in convective momentum transport (CMT) is tested for hurricane intensity forecasting using NCEP's operational Global Forecast System (GFS) and its nested Regional Spectral Model (RSM). In the parameterization the PGF is assumed to be proportional to the product of the cloud mass flux and vertical wind shear. Compared to control forecasts using the present operational GFS and RSM where the PGF effect in CMT is taken into account empirically, the new PGF parameterization helps increase hurricane intensity by reducing the vertical momentum exchange, giving rise to a closer comparison to the observations. In addition, the new PGF parameterization forecasts not only show more realistically organized precipitation patterns with enhanced hurricane intensity but also reduce the forecast track error. Nevertheless, the model forecasts with the new PGF parameterization still largely underpredict the observed intensity. One of the many possible reasons for the large underprediction may be the absence of hurricane initialization in the models.

scholarly journals Buoyancy Effect on the Flow Pattern and the Thermal Performance of an Array of Circular Cylinders

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Francesco Fornarelli ◽  
Antonio Lippolis ◽  
Paolo Oresta
Keyword(s):  
Nusselt Number ◽  
Flow Pattern ◽  
Richardson Number ◽  
Near Field ◽  
Circular Cylinders ◽  
Momentum Exchange ◽  
Force Coefficients ◽  
The Earth ◽  
Spacing Ratio ◽  
Oscillatory Character

In this paper, we found, by means of numerical simulations, a transition in the oscillatory character of the flow field for a particular combination of buoyancy and spacing in an array of six circular cylinders at a Reynolds number of 100 and Prandtl number of 0.7. The cylinders are isothermal and they are aligned with the earth acceleration (g). According to the array orientation, an aiding or an opposing buoyancy is considered. The effect of natural convection with respect to the forced convection is modulated with the Richardson number, Ri, ranging between −1 and 1. Two values of center-to-center spacing (s = 3.6d–4d) are considered. The effects of buoyancy and spacing on the flow pattern in the near and far field are described. Several transitions in the flow patterns are found, and a parametric analysis of the dependence of the force coefficients and Nusselt number with respect to the Richardson number is reported. For Ri=−1, the change of spacing ratio from 3.6 to 4 induces a transition in the standard deviation of the force coefficients and heat flux. In fact, the transition occurs due to rearrangement of the near-field flow in a more ordered wake pattern. Therefore, attention is focused on the influence of geometrical and buoyancy parameters on the heat and momentum exchange and their fluctuations. The available heat exchange models for cylinders array provide a not accurate prediction of the Nusselt number in the cases here studied.

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