scholarly journals Shock Structures Using the OBurnett Equations in Combination with the Holian Conjecture

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 427
Author(s):  
Ravi Sudam Jadhav ◽  
Amit Agrawal
Keyword(s):  
Transport Coefficients ◽  
Quantitative Agreement ◽  
Upstream Region ◽  
Shock Propagation ◽  
Wave Flow ◽  
Temperature Relation ◽  
Downstream Region ◽  
Shock Profiles ◽  
Mach Numbers ◽  
Modified Theory

In the present work, we study the normal shock wave flow problem using a combination of the OBurnett equations and the Holian conjecture. The numerical results of the OBurnett equations for normal shocks established several fundamental aspects of the equations such as the thermodynamic consistency of the equations, and the existence of the heteroclinic trajectory and smooth shock structures at all Mach numbers. The shock profiles for the hydrodynamic field variables were found to be in quantitative agreement with the direct simulation Monte Carlo (DSMC) results in the upstream region, whereas further improvement was desirable in the downstream region of the shock. For the discrepancy in the downstream region, we conjecture that the viscosity–temperature relation (μ∝Tφ) needs to be modified in order to achieve increased dissipation and thereby achieve better agreement with the benchmark results in the downstream region. In this respect, we examine the Holian conjecture (HC), wherein transport coefficients (absolute viscosity and thermal conductivity) are evaluated using the temperature in the direction of shock propagation rather than the average temperature. The results of the modified theory (OBurnett + HC) are compared against the benchmark results and we find that the modified theory improves upon the OBurnett results, especially in the case of the heat flux shock profile. We find that the accuracy gain is marginal at lower Mach numbers, while the shock profiles are described better using the modified theory for the case of strong shocks.

scholarly journals The Reporter System for GPCR Assay with the Fission YeastSchizosaccharomyces pombe

Scientifica ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Shintaro Sasuga ◽  
Toshiya Osada
Keyword(s):  
Fluorescent Protein ◽  
Signal To Noise Ratio ◽  
Biological Activities ◽  
Inducible Promoter ◽  
Upstream Region ◽  
Reporter Plasmid ◽  
Reporter System ◽  
High Background ◽  
Downstream Region ◽  
Green Fluorescent

G protein-coupled receptors (GPCRs) are associated with a great variety of biological activities. Yeasts are often utilized as a host for heterologous GPCR assay. We engineered the intense reporter plasmids for fission yeast to produce green fluorescent protein (GFP) through its endogenous GPCR pathway. As a control region of GFP expression on the reporter plasmid, we focused on seven endogenous genes specifically activated through the pathway. When upstream regions of these genes were used as an inducible promoter in combination with LPI terminator, themam2upstream region produced GFP most rapidly and intensely despite the high background. Subsequently, LPI terminator was replaced with the corresponding downstream regions. The SPBC4.01 downstream region enhanced the response with the low background. Furthermore, combining SPBC4.01 downstream region with the sxa2 upstream region, the signal to noise ratio was obviously better than those of other regions. We also evaluated the time- and dose-dependent GFP productions of the strains transformed with the reporter plasmids. Finally, we exhibited a model of simplified GPCR assay with the reporter plasmid by expressing endogenous GPCR under the control of the foreign promoter.

Reynolds stresses and mean fields generated by pure waves: applications to shear flows and convection in a rotating shell

2008 ◽  
Vol 602 ◽  
pp. 303-326 ◽  
Author(s):  
E. PLAUT ◽  
Y. LEBRANCHU ◽  
R. SIMITEV ◽  
F. H. BUSSE
Keyword(s):  
Shear Flows ◽  
Rossby Waves ◽  
Zonal Flow ◽  
Quantitative Agreement ◽  
Model Systems ◽  
Geometrical Factor ◽  
Wave Flow ◽  
Nonlinear Frequency ◽  
Two Dimensional ◽  
Reynolds Stresses

A general reformulation of the Reynolds stresses created by two-dimensional waves breaking a translational or a rotational invariance is described. This reformulation emphasizes the importance of a geometrical factor: the slope of the separatrices of the wave flow. Its physical relevance is illustrated by two model systems: waves destabilizing open shear flows; and thermal Rossby waves in spherical shell convection with rotation. In the case of shear-flow waves, a new expression of the Reynolds–Orr amplification mechanism is obtained, and a good understanding of the form of the mean pressure and velocity fields created by weakly nonlinear waves is gained. In the case of thermal Rossby waves, results of a three-dimensional code using no-slip boundary conditions are presented in the nonlinear regime, and compared with those of a two-dimensional quasi-geostrophic model. A semi-quantitative agreement is obtained on the flow amplitudes, but discrepancies are observed concerning the nonlinear frequency shifts. With the quasi-geostrophic model we also revisit a geometrical formula proposed by Zhang to interpret the form of the zonal flow created by the waves, and explore the very low Ekman-number regime. A change in the nature of the wave bifurcation, from supercritical to subcritical, is found.

Active Vibration Control of the Axially Moving String Using Space Feedforward and Feedback Controllers

1996 ◽  
Vol 118 (3) ◽  
pp. 306-312 ◽  
Author(s):  
S. Ying ◽  
C. A. Tan
Keyword(s):  
Vibration Control ◽  
Feedforward Control ◽  
Active Vibration Control ◽  
Upstream Region ◽  
Control Force ◽  
Feedback Controllers ◽  
Axially Moving String ◽  
Downstream Region ◽  
Active Vibration ◽  
Axially Moving

Active vibration control of an axially moving string using space feedforward and feedback controllers is presented. Closed-form results for the transverse response of both the uncontrolled and controlled string are given in the s domain. The space feedforward controller is established by employing the idea of wave cancellation. The proposed control law indicates that vibration in the region downstream of the control force can be cancelled. With the space feedforward control, the mode shapes of the axially moving string are changed such that the free response tends to zero in the downstream region. An interesting physical interpretation is that the control force acts effectively as a holder (active support) which limits the vibration of the string to the upstream region and eliminates any vibration in the downstream region. Simulation results show that the response of the string to both sinusoidal and random excitations is suppressed by applying the space feedforward control. The feedback controller is introduced to attenuate the response of the string due to undesired disturbances in the downstream.

scholarly journals A deep insight into the ion foreshock with the help of test particle two-dimensional simulations

2020 ◽  
Vol 38 (6) ◽  
pp. 1217-1235
Author(s):  
Philippe Savoini ◽  
Bertrand Lembège
Keyword(s):  
Electric Field ◽  
Shock Front ◽  
Test Particle ◽  
Field Component ◽  
Upstream Region ◽  
Mirror Reflection ◽  
Two Dimensional ◽  
Shock Profiles ◽  
The Impact

Abstract. Two-dimensional (2D) test particle simulations based on shock profiles issued from 2D full particle-in-cell (PIC) simulations are used in order to analyze the formation processes of ions back streaming within the upstream region after interacting with a quasi-perpendicular curved shock front. Two different types of simulations have been performed based on (i) a fully consistent expansion (FCE) model, which includes all self-consistent shock profiles at different times, and (ii) a homothetic expansion (HE) model in which shock profiles are fixed at certain times and artificially expanded in space. The comparison of both configurations allows one to analyze the impact of the front nonstationarity on the back-streaming population. Moreover, the role of the space charge electric field El is analyzed by either including or canceling the El component in the simulations. A detailed comparison of these last two different configurations allows one to show that this El component plays a key role in the ion reflection process within the whole quasi-perpendicular propagation range. Simulations provide evidence that the different field-aligned beam (FAB) and gyro-phase bunched (GPB) populations observed in situ are essentially formed by a Et×B drift in the velocity space involving the convective electric field Et. Simultaneously, the study emphasizes (i) the essential action of the magnetic field component on the GPB population (i.e., mirror reflection) and (ii) the leading role of the convective field Et in the FAB energy gain. In addition, the electrostatic field component El is essential for reflecting ions at high θBn angles and, in particular, at the edge of the ion foreshock around 70∘. Moreover, the HE model shows that the rate BI% of back-streaming ions is strongly dependent on the shock front profile, which varies because of the shock front nonstationarity. In particular, reflected ions appear to escape periodically from the shock front as bursts with an occurrence time period associated to the self-reformation of the shock front.

scholarly journals Improved theory for shock waves using the OBurnett equations

2021 ◽  
Vol 929 ◽  
Author(s):  
Ravi Sudam Jadhav ◽  
Abhimanyu Gavasane ◽  
Amit Agrawal
Keyword(s):  
Shock Waves ◽  
Stokes Equations ◽  
Direct Simulation Monte Carlo ◽  
Space Velocity ◽  
Navier Stokes ◽  
Wave Flow ◽  
Complex Flow ◽  
Navier Stokes Equations ◽  
Wide Range ◽  
Mach Numbers

The main goal of the present study is to thoroughly test the recently derived OBurnett equations for the normal shock wave flow problem for a wide range of Mach number ( $3 \leq Ma \leq 9$ ). A dilute gas system composed of hard-sphere molecules is considered and the numerical results of the OBurnett equations are validated against in-house results from the direct simulation Monte Carlo method. The primary focus is to study the orbital structures in the phase space (velocity–temperature plane) and the variation of hydrodynamic fields across the shock. From the orbital structures, we observe that the heteroclinic trajectory exists for the OBurnett equations for all the Mach numbers considered, unlike the conventional Burnett equations. The thermodynamic consistency of the equations is also established by showing positive entropy generation across the shock. Further, the equations give smooth shock structures at all Mach numbers and significantly improve upon the results of the Navier–Stokes equations. With no tweaking of the equations in any way, the present work makes two important contributions by putting forward an improved theory of shock waves and establishing the validity of the OBurnett equations for solving complex flow problems.

Laser anemometer study of flow development in curved circular pipes

1978 ◽  
Vol 85 (3) ◽  
pp. 497-518 ◽  
Author(s):  
Y. Agrawal ◽  
L. Talbot ◽  
K. Gong
Keyword(s):  
Axial Velocity ◽  
Three Dimensional ◽  
Quantitative Agreement ◽  
Upstream Region ◽  
Uniform Motion ◽  
Dean Number ◽  
Number Range ◽  
Curved Pipe ◽  
Laser Anemometry ◽  
Pipe Radius

An experimental investigation was carried out of the development of steady, laminar, incompressible flow of a Newtonian fluid in the entry region of a curved pipe for the entry condition of uniform motion. Two semicircular pipes of radius ratios 1/20 and 1/7 were investigated, covering a Dean number range from 138 to 679. The axial velocity and the component of secondary velocity parallel to the plane of curvature of the pipe were measured using laser anemometry. It was observed that, in the upstream region where the boundary layers are thin compared with the pipe radius, the axial velocity within the irrotational core first develops to form a vortex-like flow. In the downstream region, characterized by viscous layers of thickness comparable with the pipe radius, there appears to be three-dimensional separation at the inner wall. There is also an indication of an additional vortex structure embedded within the Dean-type secondary motion. The experimental axial velocity profiles are compared with those constructed from the theoretical analyses of Singh and Yao & Berger. The quantitative agreement between theory and experiment is found to be poor; however, some of the features observed in the experiment are in qualitative agreement with the theoretical solution of Yao & Berger.

Results and Analysis of Implicit Large Eddy Simulations of Equilibrium Spatially Developing Turbulent Boundary Layers at Multiple Mach Numbers

2014 ◽  
Author(s):  
Mbu Waindim ◽  
Datta V. Gaitonde
Keyword(s):  
Boundary Layers ◽  
Plate Boundary ◽  
Large Eddy Simulations ◽  
Upstream Region ◽  
Computational Domain ◽  
Turbulent Characteristics ◽  
Large Eddy ◽  
Mach Numbers ◽  
Dimensional Simulation ◽  
Invariant Statistics

Equilibrium turbulent flat plate boundary layers with time invariant statistics were obtained at Mach numbers 1.7, 2.3, and 2.9. These are to be used as the initial condition for Large Eddy Simulations (LES) or Direct Numerical Simulations (DNS) of shock wave/turbulent boundary layer interactions utilizing a body force-based method. The results obtained are supplemented by an analysis of the mean and statistical properties of the respective boundary layers. The spanwise extent of the domain required to allow adequate decorrelation between the centerline and the boundaries is investigated by extensively probing the flowfields obtained. This is done to quantify the coherent structures of the turbulent flow. Specifically, two point correlations and integral length scales are used to investigate spanwise decorrelation distances in an attempt to pick a computational domain which is large enough to permit decorrelation downstream but small enough to minimize computational costs. It is shown that by examining the precursor events in the upstream region, namely the generalized stability criterion, it is possible to provide estimates for the force field parameters necessary for transition for a given flow, with only a small portion of the domain in the neighborhood of the trip. The technique is made even more efficient by investigating the possibility of determining these parameters using a two-dimensional simulation. Additionally, the three flow fields obtained are surveyed to confirm that they are suitable for subsequent SBLI simulations. We check that (i)they possess the expected turbulent characteristics and (ii)there is no signature of the tripping mechanism.

Optimization of Single Row Jet Impingement Array by Varying Flow Rates

2013 ◽  
Author(s):  
Nicholas Miller ◽  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Jet Impingement ◽  
Upstream Region ◽  
Channel Height ◽  
Transfer Performance ◽  
Mean Velocity ◽  
Flow Rates ◽  
Downstream Region ◽  
High Heat Transfer

The current detailed experimental study focuses on the optimization of heat transfer performance through jet impingement by varying the coolant flow rate to each individual jet. The test section consists of an array of five jets, which is individually fed and metered separately, and expels air through one exit. The jet diameter D, channel height to jet diameter H/D, and jet spacing to diameter S/D, are all held constant at 9.53 mm (0.375 in), 2 and 4 respectively. The Reynolds number, which is based on jet diameter and bulk mean velocity at each jet, ranges from 50,000 to 80,000. A transient liquid crystal technique is employed in this study to determine the local and overall-average heat transfer coefficient distribution on the target plate. Commercially available CFD software, ANSYS CFX, is used to qualitatively correlate the experimental results and to provide detailed insights of the flow field created by the array of jets. The results revealed higher heat transfer coefficients in the impingement area, while decreasing in the radial direction. The upstream region exhibited high heat transfer performance, which is ultimately driven by the jet impingement from the first jet to the third jet. Heat transfer performance decreases at the downstream region with the development of cross-flow. By varying the jet flow rates at approximately ±2%, local heat transfer at the downstream region is elevated and the total heat transfer enhancement on the target surface is enhanced up to 35% compared to the baseline case.

scholarly journals Simulation of Actual Evapotranspiration and Evaluation of Three Complementary Relationships in the Upper Regions of the Mekong River and the Salween River

2021 ◽  
Author(s):  
Yongshan Jiang ◽  
Zhaofei Liu ◽  
Rui Wang ◽  
Pingcuo Gele
Keyword(s):  
Wind Speed ◽  
River Basin ◽  
Negative Correlation ◽  
Aridity Index ◽  
Actual Evapotranspiration ◽  
Upstream Region ◽  
Contribution Rate ◽  
Complementary Relationship ◽  
Annual Series ◽  
Downstream Region

Abstract Based on observed precipitation and runoff data, monthly actual evapotranspiration (ETa) was calculated by the hydrological budget balance method in the Nu River Basin (NRB) and Lancang River Basin (LCRB). The performance of three developed complementary relationship methods, the nonlinear advection-aridity (nonlinear AA) method, generalized complementary relationship method (B2015), and sigmoid generalized complementary function (H2018), on simulating (ETa) were evaluated. The evaluation results showed that three methods were able to accurately simulate monthly (ETa) series. The NSE between the monthly (ETa) simulated by the nonlinear AA, B2015, and H2018 methods and the water-balance-derived (ETa) were 0.89, 0.83, and 0.91, respectively. The R-square were 0.90, 0.84, and 0.93, respectively. Overall, the H2018 method showed the best performance. The parameter α had a negative correlation with regional aridity index. Annual (ETa) and precipitation showed significant increasing trends during 1956–2018 in the basins at all temporal scales (dry and wet seasons and annual series). Runoff also exhibited an increasing trend in each sub-basin, except for the downstream region of the LCRB. The increasing magnitudes of wet reason precipitation and runoff in the mid-stream region was the highest, with the value of 73.7 mm/10a and 44.9 mm/10a, respectively. The (ETa) increased dramatically in the downstream region, the magnitude reached 25.9 mm/10a. Precipitation was the main factor leasing to (ETa) change. The increasing magnitude of (ETa) accounted for 42.4% of the precipitation increment. Research on the influence mechanism between meteorological factors and (ETa) showed that the contribution rate of air temperature to (ETa) was the highest, reaching 23.5%, which showed a significant positive correlation. The second was wind speed, whose contribution rate was − 10.2% on average, and even reached − 14.1% in the upstream region of the NRB. The correlation coefficient between (ETa) and wind speed was highest in mid-stream region of the NRB, which was greater than 0.80. The contribution rates of increasing humidity to (ETa) were − 12.5% and − 9.2% in the NRB and LCRB, respectively. (ETa) was negatively correlated with humidity. The negative correlation was especially strong in the mid-stream region, with coefficients were greater than − 0.65. The sunshine hours had the least effect on (ETa), and the contribution rates were − 6.5% and − 4.1%, respectively.

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