High-resolution simulations of cylindrical gravity currents in a rotating system

2016 ◽  
Vol 806 ◽  
pp. 71-101 ◽  
Author(s):  
Albert Dai ◽  
Ching-Sen Wu
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
Potential Energy ◽  
Three Dimensional ◽  
Gravity Currents ◽  
The Body ◽  
Heavy Fluid ◽  
Rotating System ◽  
Maximum Radius ◽  
Inertia Forces

Cylindrical gravity currents, produced by a full-depth lock release, in a rotating system are investigated by means of three-dimensional high-resolution simulations of the incompressible variable-density Navier–Stokes equations with the Coriolis term and using the Boussinesq approximation for a small density difference. Here, the depth of the fluid is chosen to be the same as the radius of the cylindrical lock and the ambient fluid is non-stratified. Our attention is focused on the situation when the ratio of Coriolis to inertia forces is not large, namely $0.1\leqslant {\mathcal{C}}\leqslant 0.3$, and the non-rotating case, namely ${\mathcal{C}}=0$, is also briefly considered. The simulations reproduce the major features observed in the laboratory and provide more detailed flow information. After the heavy fluid contained in a cylindrical lock is released in a rotating system, the influence of the Coriolis effects is not significant during the initial one-tenth of a revolution of the system. During the initial one-tenth of a revolution of the system, Kelvin–Helmholtz vortices form and the rotating cylindrical gravity currents maintain nearly perfect axisymmetry. Afterwards, three-dimensionality of the flow quickly develops and the outer rim of the spreading heavy fluid breaks away from the body of the current, which gives rise to the maximum dissipation rate in the system during the entire adjustment process. The detached outer rim of heavy fluid then continues to propagate outward until a maximum radius of propagation is attained. The body of the current exhibits a complex contraction–relaxation motion and new outwardly propagating pulses form regularly in a period slightly less than half-revolution of the system. Depending on the ratio of Coriolis to inertia forces, such a contraction–relaxation motion may be initiated after or before the attainment of a maximum radius of propagation. In the contraction–relaxation motion of the heavy fluid, energy is transformed between potential energy and kinetic energy, while it is mainly the kinetic energy that is consumed by the dissipation. As a new pulse initially propagates outward, the potential energy in the system increases at the expense of decreasing kinetic energy, until a local maximum of potential energy is reached. During the latter part of the new pulse propagation, the kinetic energy in the system increases at the expense of decreasing potential energy, until a local minimum of potential energy is reached and another new pulse takes form. With the use of three-dimensional high-resolution simulations, the lobe-and-cleft structure at the advancing front can be clearly observed. The number of lobes is maintained only for a limited period of time before merger between existing lobes occurs when a maximum radius of propagation is approached. The high-resolution simulations complement the existing shallow-water formulation, which accurately predicts many important features and provides insights for rotating cylindrical gravity currents with good physical assumptions and simple mathematical models.

scholarly journals POLA LUKA PADA KEMATIAN AKIBAT PANAH WAYER DI RSUP PROF. DR. R. D. KANDOU MANADO PERIODE JANUARI SAMPAI OKTOBER 2014

e-CliniC ◽  
2015 ◽  
Vol 3 (2) ◽  
Author(s):  
Jaysen Kobstan ◽  
Johannis F. Mallo ◽  
Djemi Tomuka
Keyword(s):  
Retrospective Study ◽  
Kinetic Energy ◽  
Potential Energy ◽  
The Body ◽  
Pattern Of Injury ◽  
Vital Part ◽  
Penetrating Wound

Abstract: Panah wayer (a kind of arrow) has become a troubling incident for the citizen of Manado City. People are afraid to do activities outside, especially at night. Wound that caused by this arrow often leads to death if it is punctured into a vital part of the body. However, there are also surviving victims. This study aimed to obtain the pattern of injuries in dead victims caused by this panah wayer. This was a descriptive and retrospective study using visum et repertum as pimary data. The results showed that injuries caused by panah wayer had diverse sizes and depths, depend on the kinetic energy of the arrow itself and the potential energy of the sling itself. Injuries that caused by panah wayer look like a penetrating wound and the hook-like structure at its tip made this arrow hard to repeal and if it is pulled out forcefully a wider rupture at the area of injury can occur.Keywords: pattern of injury, panah wayerAbstrak: Panah wayer telah meresahkan warga kota Manado dan mengakibatkan ketakutan untuk beraktifitas di luar rumah, terutama di malam hari. Luka akibat panah wayer umumnya mengarah pada kematian bila tertusuk di daerah-daerah tertentu pada bagian tubuh. Penelitian ini bertujuan untuk mendapatkan pola luka pada kematian akibat panah wayer. Penelitian ini bersifat deskriptif retrospektif dengan meggunakan visum et repertum sebagai data primer. Hasil penelitian memperlihatkan bahwa luka akibat panah wayer memiliki ukuran dan kedalaman luka yang beragam berdasarkan energi kinetik dari panah wayer itu sendiri dan energi potensial dari pelontar. Luka yang disebabkan panah wayer memiliki bentuk seperti luka tusuk dan struktur seperti pengait yang terdapat di bagian ujung panah wayer meyebabkan panah wayer sulit untuk dicabut dan jika dicabut secara paksa akan menimbulkan robekan yang lebih besar pada daerah luka.Kata kunci: pola luka, panah wayer

On the formation and propagation of nonlinear internal boluses across a shelf break

2007 ◽  
Vol 577 ◽  
pp. 137-159 ◽  
Author(s):  
SUBHAS K. VENAYAGAMOORTHY ◽  
OLIVER B. FRINGER
Keyword(s):  
High Resolution ◽  
Gravity Waves ◽  
Three Dimensional ◽  
Internal Gravity Waves ◽  
Gravity Currents ◽  
Interaction Process ◽  
Shelf Break ◽  
Ambient Fluid ◽  
Dense Fluid ◽  
Incident Waves

High-resolution two- and three-dimensional numerical simulations are performed of first-mode internal gravity waves interacting with a shelf break in a linearly stratified fluid. The interaction of nonlinear incident waves with the shelf break results in the formation of upslope-surging vortex cores of dense fluid (referred to here as internal boluses) that propagate onto the shelf. This paper primarily focuses on understanding the dynamics of the interaction process with particular emphasis on the formation, structure and propagation of internal boluses onshelf. A possible mechanism is identified for the excitation of vortex cores that are lifted over the shelf break, from where (from the simplest viewpoint) they essentially propagate as gravity currents into a linearly stratified ambient fluid.

Axisymmetric gravity currents in a rotating system: experimental and numerical investigations

2001 ◽  
Vol 447 ◽  
pp. 1-29 ◽  
Author(s):  
MARK A. HALLWORTH ◽  
HERBERT E. HUPPERT ◽  
MARIUS UNGARISH
Keyword(s):  
Flow Field ◽  
Shallow Water ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Salt Water ◽  
Gravity Currents ◽  
The Body ◽  
Water Model ◽  
Maximum Radius ◽  
Theoretical Predictions

The propagation at high Reynolds number of a heavy, axisymmetric gravity current of given initial volume over a horizontal boundary is considered in both rotating and non-rotating situations. The investigation combines experiments with theoretical predictions by both shallow-water approximations and numerical solutions of the full axisymmetric equations. Attention is focused on cases when the initial ratio of Coriolis to inertia forces is small. The experiments were performed by quickly releasing a known cylindrical volume of dense salt water of 2 m diameter at the centre of a circular tank of diameter 13 m containing fresh ambient water of typical depth 80 cm. The propagation of the current was recorded for different initial values of the salt concentration, the volume of released fluid, the ratio of the initial height of the current to the ambient depth, and the rate of rotation. A major feature of the rotating currents was the attainment of a maximum radius of propagation. Thereafter a contraction–relaxation motion of the body of fluid and a regular series of outwardly propagating pulses was observed. The frequency of these pulses is slightly higher than inertial, and the amplitude is of the order of magnitude of half the maximum radius. Theoretical predictions of the corresponding gravity currents were also obtained by (i) previously developed shallow-water approximations (Ungarish & Huppert 1998) and (ii) a specially developed finite-difference code based on the full axisymmetric Navier–Stokes equations. The ‘numerical experiments’ provided by this code are needed to capture details of the flow field (such as the non-smooth shape of the interface, the vertical dependence of the velocity field) which are not reproduced by the shallow-water model and are very difficult for, or outside the range of, accurate experimental measurement. The comparisons and discussion provide insight into the flow field and indicate the advantages and limitations of the verified simulation tools.

Three-dimensional kinematics and limb kinetic energy of running cockroaches.

1997 ◽  
Vol 200 (13) ◽  
pp. 1919-1929 ◽  
Author(s):  
R Kram ◽  
B Wong ◽  
R J Full
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Three Dimensional ◽  
The Body ◽  
Morphological Data ◽  
Fast Running ◽  
Total Mechanical Energy ◽  
Reaction Forces

We tested the hypothesis that fast-running hexapeds must generate high levels of kinetic energy to cycle their limbs rapidly compared with bipeds and quadrupeds. We used high-speed video analysis to determine the three-dimensional movements of the limbs and bodies of cockroaches (Blaberus discoidalis) running on a motorized treadmill at 21 cm s-1 using an alternating tripod gait. We combined these kinematic data with morphological data to calculate the mechanical energy produced to move the limbs relative to the overall center of mass and the mechanical energy generated to rotate the body (head + thorax + abdomen) about the overall center of mass. The kinetic energy involved in moving the limbs was 8 microJ stride-1 (a power output of 21 mW kg-1, which was only approximately 13% of the external mechanical energy generated to lift and accelerate the overall center of mass at this speed. Pitch, yaw and roll rotational movements of the body were modest (less than +/- 7 degrees), and the mechanical energy required for these rotations was surprisingly small (1.7 microJ stride-1 for pitch, 0.5 microJ stride-1 for yaw and 0.4 microJ stride-1 for roll) as was the power (4.2, 1.2 and 1.1 mW kg-1, respectively). Compared at the same absolute forward speed, the mass-specific kinetic energy generated by the trotting hexaped to swing its limbs was approximately half of that predicted from data on much larger two- and four-legged animals. Compared at an equivalent speed (mid-trotting speed), limb kinetic energy was a smaller fraction of total mechanical energy for cockroaches than for large bipedal runners and hoppers and for quadrupedal trotters. Cockroaches operate at relatively high stride frequencies, but distribute ground reaction forces over a greater number of relatively small legs. The relatively small leg mass and inertia of hexapeds may allow relatively high leg cycling frequencies without exceptionally high internal mechanical energy generation.

Passage Flow Structure and its Influence on Endwall Heat Transfer in a 90° Turning Duct: Turbulent Stresses and Turbulent Kinetic Energy Production

1996 ◽  
Author(s):  
Brian G. Wiedner ◽  
Cengiz Camci
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
High Resolution ◽  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Flow Structure ◽  
Three Dimensional ◽  
Duct Flow ◽  
Turbulent Flow Field

The complex interaction between three-dimensional passage flow structure and endwall convective heat transfer in a square cross section, 90° turbulent duct flow has been experimentally investigated. Fine details of the momentum and heat transport process in a laboratory model that simulated a high Reynolds number three-dimensional passage flow are presented. The specific flow and heat transfer mechanisms are frequently encountered in the hot mainstream of axial flow turbines and internal coolant passages. Similar physical phenomena may also be observed in many other fluid machinery systems. The mean radius to duct width ratio was 2.3 and the Reynolds number based on inlet center line velocity, duct width, and ambient conditions was approximately 360,000. The complete Reynolds stress tensor was measured using a triple sensor hot wire. The turbulent normal and shear stresses, turbulent kinetic energy, and production of turbulent kinetic energy are presented. A steady state heat flux measurement technique and liquid crystal thermography were used to determine the character of the endwall heat transfer in the form of a high resolution heat transfer map. The flow field was dominated by strong counter rotating secondary flows characteristic of 90° turning ducts. The flow structure also included areas of strong streamwise accelerations and decelerations, high vorticity, local regions of significant total pressure loss, and a complex turbulent flow field structure. The development of the turbulent features of the 90° turning duct flow field and the influence of the turbulent flow field on the endwall convective heat transfer distribution are discussed. The multi-dimensional flow and high resolution heat transfer results are currently being incorporated in computational aerothermal models under development at Penn State University. The results are also available as a data base for future aerothermal model validation studies.

Forces and Moments on a Small Body Moving in a 3-D Unsteady Flow (With Applications to Slender Structures)

1993 ◽  
Vol 115 (2) ◽  
pp. 91-104 ◽  
Author(s):  
L. Foulhoux ◽  
M. M. Bernitsas
Keyword(s):  
Unsteady Flow ◽  
Small Body ◽  
Three Dimensional ◽  
Field Approximation ◽  
The Body ◽  
Body Motion ◽  
Inertia Force ◽  
Six Degree Of Freedom ◽  
Polynomial Expansions ◽  
Inertia Forces

Complete expressions are derived for the inertia forces and moments acting on a small body in a six-degree-of-freedom motion in a three-dimensional unsteady flow in an unbounded ideal fluid. The far-field approximation of the body motion is represented by a series of multipoles located at the origin of the body. Unsteady terms are expanded in a dual series to the multipole series. Lagally integrals are expressed in terms of multipoles as well, by using Legendre polynomial expansions. New inertia force expressions are derived by truncating the multipole series after the quadrupoles. Corresponding terms for moments are also developed. The derived formulas are still compact enough for engineering applications. Many practical problems involving fixed and oscillating cylinders, piles, and risers are studied numerically. Comparisons to the Morison equation formulation prove that the nonlinear convective terms are not negligible in multidimensional relative flows.

Mechanical Energy Expenditures and Movement Efficiency in Full Body Reaching Movements

2010 ◽  
Vol 26 (1) ◽  
pp. 32-44 ◽  
Author(s):  
Daohang Sha ◽  
Christopher R. France ◽  
James S. Thomas
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Target Location ◽  
Mechanical Energy ◽  
The Body ◽  
Reaching Movements ◽  
Whole Body ◽  
Joint Power ◽  
Total Mechanical Energy ◽  
Full Body

The effect of target location, speed, and handedness on the average total mechanical energy and movement efficiency is studied in 15 healthy subjects (7 males and 8 females with age 22.9 ± 1.79 years old) performing full body reaching movements. The average total mechanical energy is measured as the time average of integration of joint power, potential energy, and kinetic energy respectively. Movement efficiency is calculated as the ratio of total kinetic energy to the total joint power and potential energy. Results show that speed and target location have significant effects on total mechanical energy and movement efficiency, but reaching hand only effects kinetic energy. From our findings we conclude that (1) efficiency in whole body reaching is dependent on whether the height of the body center of mass is raised or lowered during the task; (2) efficiency is increased as movement speed is increased, in part because of greater changes in potential energy; and (3) the CNS does not appear to use movement efficiency as a primary planning variable in full body reaching. It may be dependent on a combination of other factors or constraints.

scholarly journals Propelling and perturbing appendages together facilitate strenuous ground self-righting

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Ratan Othayoth ◽  
Chen Li
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Landscape ◽  
The Body ◽  
Body Motion ◽  
Physical Interaction ◽  
Landscape Model ◽  
High Pitch ◽  
Potential Energy Landscape ◽  
Do So

Terrestrial animals must self-right when overturned on the ground, but this locomotor task is strenuous. To do so, the discoid cockroach often pushes its wings against the ground to begin a somersault which rarely succeeds. As it repeatedly attempts this, the animal probabilistically rolls to the side to self-right. During winged self-righting, the animal flails its legs vigorously. Here, we studied whether wing opening and leg flailing together facilitate strenuous ground self-righting. Adding mass to increase hind leg flailing kinetic energy increased the animal’s self-righting probability. We then developed a robot with similar strenuous self-righting behavior and used it as a physical model for systematic experiments. The robot’s self-righting probability increased with wing opening and leg flailing amplitudes. A potential energy landscape model revealed that, although wing opening did not generate sufficient kinetic energy to overcome the high pitch potential energy barrier to somersault, it reduced the barrier for rolling, facilitating the small kinetic energy from leg flailing to probabilistically overcome it to self-right. The model also revealed that the stereotyped body motion during self-righting emerged from physical interaction of the body and appendages with the ground. Our work demonstrated the usefulness of potential energy landscape for modeling self-righting transitions.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

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