Flow regimes and energy loss on chutes with upward inclined steps

2004 ◽  
Vol 31 (5) ◽  
pp. 870-879 ◽  
Author(s):  
Chaiyuth Chinnarasri ◽  
Somchai Wongwises
Keyword(s):  
Experimental Data ◽  
Energy Dissipation ◽  
Kinetic Energy ◽  
Energy Loss ◽  
Dimensional Analysis ◽  
Water Flow ◽  
Empirical Equation ◽  
Loss Ratio ◽  
Empirical Correlations ◽  
Drop Number

This paper presents new experimental data on water flow on stepped chutes with upward inclined steps. The slopes of the chutes are 30°, 45°, and 60° whereas the upward angles of the inclined steps are 10°, 20°, and 30°, respectively. Classifications of flow patterns by empirical correlations are presented. Based on dimensional analysis, the important parameters are analyzed, and the relevant dimensionless parameters are established. The energy loss and outlet velocity are strongly influenced by the Drop number and the slope of the stepped chutes. As the Drop number increases, the energy loss ratio decreases. At identical Drop numbers the energy loss ratio on the more moderate slope is greater than on the steeper. The adverse slope of the inclined steps increases the energy loss ratio and decreases the outlet velocity by less than 10%. To estimate the kinetic energy ratio, an empirical equation is proposed.Key words: stepped chutes, inclined step, energy dissipation, skimming flow, spillways.

scholarly journals Numerical modelling of transonic centripetal flow in radial turbine blade cascade

2018 ◽  
Vol 168 ◽  
pp. 02008
Author(s):  
Petr Straka
Keyword(s):  
Experimental Data ◽  
Kinetic Energy ◽  
Numerical Modelling ◽  
Energy Loss ◽  
Linear Representation ◽  
Buffer Zone ◽  
Blade Cascade ◽  
Radial Turbine ◽  
Paper Method ◽  
Kinetic Energy Loss

Numerical modelling of transonic centripetal turbulent flow in radial blade cascade is described in this paper. Method of the confusor buffer zone is applied to overcome some numerical obstacles related with specifical properties of the outlet confusor. Kinetic energy loss coeficient of the radial blade cascade is compared with its linear representation and with experimental data.

Abstract 105: Increased Dynamic Mechanical Energy Dissipation in Human Abdominal Aortic Aneurysm

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Doran S Mix ◽  
Ibrahima Bah ◽  
Sandra A Toth ◽  
Michael C Stoner ◽  
Adam J Doyle ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Energy Loss ◽  
Mechanical Testing ◽  
Mechanical Energy ◽  
Aortic Aneurysms ◽  
Aortic Tissue ◽  
Loss Ratio ◽  
Tissue Viability ◽  
Static Modulus ◽  
Abdominal Aortic

Objectives: Individualized patient rupture risk for abdominal aortic aneurysms (AAA) remains elusive due to a limited understanding of the biomechanical events that trigger aneurysm growth and aortic wall failure. To date there has been a paucity of data describing how physiologic pulsatile energy is stored (E') and lost (E'') from AAA tissue. Our hypothesis is that AAA tissue dissipates more cyclic energy at a physiologic frequency, as determined by (E''/ E'), when compared to healthy aortic tissue. Methods: Human healthy aortic and AAA samples were obtained from cadaveric and surgical specimens. Specimens were stored at 4 o C in 0.9%NS and mechanically tested within 36 hrs of explant. Uniaxial mechanical testing (ADMET BioTense) was performed in the circumferential orientation with the tissue pre-loaded to an equivalent physiologic stress of a 5 cm at a 110 mmHg mean pressure. A sinusoidal ±5% strain was applied at 1 Hz for 40 cycles with simultaneous force measurements. After mechanical testing, immunohistochemical staining was performed to confirm tissue viability. Results: AAA tissue was significantly stiffer when compared to healthy aorta, as demonstrated by a greater average static modulus (E) 1555.4 ± 384 vs. 970 ± 128 kPa (n=5, p=0.03). Dynamic testing of the AAA tissue noted a significantly greater energy loss (E'') 137.8±36.7 vs. 43.1±21.7 (p<0.01) and loss ratio (E''/ E') 0.090 ± 0.023 vs. 0.044 ± 0.023 (p=0.02), when compared to normal specimens. Figure #1 compares the static modulus (E) to the loss ratio (E''/ E') for the aortic tissue specimens. Histologic analysis confirmed tissue viability during of all specimens. Conclusions: Our data demonstrates that AAA tissue dissipates more energy (E'') and has a greater energy loss ratio (E''/ E'), suggesting that more pulsatile energy is dissipated in diseased tissue. Future work is needed to determine how this energy dissipation influences the biologic pathogenesis of AAA growth and rupture.

scholarly journals Study of Energy Dissipation of Pooled Stepped Spillways

2016 ◽  
Vol 2 (5) ◽  
pp. 208-220 ◽  
Author(s):  
Khosro Morovati ◽  
Afshin Eghbalzadeh ◽  
Saba Soori
Keyword(s):  
Experimental Data ◽  
Energy Dissipation ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Relative Energy ◽  
Turbulence Simulation ◽  
Stepped Spillways ◽  
Flow Surface ◽  
Flow Turbulence ◽  
Rng Turbulence Model

Water transferring to the dam downstream creates high levels of kinetic energy. Stepped spillways are amongst the most effective spillways in reducing the kinetic energy of the flow moving towards the downstream. The geometry of the steps in stepped spillways can affect the reduction of kinetic energy of the flow transferring to the downstream. Therefore, in this study the effect of different number of steps and discharge on flow pattern especially energy dissipation were investigated. The VOF method was used to simulate the flow surface and the k-ε (RNG) turbulence model was used for flow turbulence simulation. Comparing the results obtained from the numerical simulation with the experimental data indicated an acceptable level of consistency. Comparing the obtained results showed that decreasing the number of the steps of pooled stepped spillways reduced flow velocity and increased the relative energy dissipation at the end of the spillway. Decreasing the number of steps increased the turbulent kinetic energy value. Also, the maximum turbulent kinetic energy was obtained near the step’s pool. Moreover the results indicated that the value of turbulent kinetic energy increased along the spillway. 

Numerical investigation of energy loss in a centrifugal pump through kinetic energy dissipation theory

2020 ◽  
Vol 234 (19) ◽  
pp. 3745-3761
Author(s):  
Fen Lai ◽  
Xiangyuan Zhu ◽  
Guojun Li
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Flow Field ◽  
Energy Loss ◽  
Unsteady Flow ◽  
Turbulent Kinetic Energy ◽  
Centrifugal Pump ◽  
Cross Section ◽  
Three Dimensional ◽  
Near Wall

In this study, energy loss within a centrifugal pump is investigated by post-processing three-dimensional unsteady flow field through kinetic energy dissipation theory. The three-dimensional unsteady flow field is predicted by solving unsteady Reynolds-averaged Navier–Stokes equations. The kinetic energy dissipation consists of three parts: averaged kinetic energy dissipation, turbulent kinetic energy dissipation, and near-wall revised kinetic energy dissipation. The total value variations of three kinetic energy dissipations in the centrifugal pump with flowrate are investigated and compared. Results show that with the increase in flowrate, the total near-wall revised kinetic energy dissipation gradually increases, the total turbulent kinetic energy dissipation first gradually decreases and then gradually increases, and reaches the minimum value at the design flowrate. The total averaged kinetic energy dissipation is less than the total turbulent and the total near-wall revised kinetic energy dissipations, and the total near-wall revised kinetic energy dissipation is larger than the total turbulent kinetic energy dissipation when the flowrate is larger than 0.75 Qdes. The space variation of the near-wall revised kinetic energy dissipation with flowrate shows that large near-wall revised kinetic energy dissipation mainly occurs at the volute and transfers from the small cross-section casing to large cross-section casing and discharge pipe with the increase in flowrate. The space variations of the turbulent kinetic energy dissipation with time for three flowrates are also discussed. Results indicate that large turbulent kinetic energy dissipation near the volute tongue evidently changes with the rotation of the impeller, particularly in 0.5 Qdes. The large turbulent kinetic energy dissipation gradually expands to the pressure side of the blade when the volute tongue gradually approaches the middle of the impeller blade passage. The large turbulent kinetic energy dissipation transfers from the impeller inlet and outlet to the volute tongue and discharge pipe with the increase in flowrate. The findings of this study can serve as guide to improve the design of centrifugal pumps.

Semi-Empirical Approach for Fission Fragment Energy Degradation in any Elementary Medium

1971 ◽  
Vol 49 (23) ◽  
pp. 3036-3040 ◽  
Author(s):  
M. Hakim ◽  
N. H. Shafrir
Keyword(s):  
Experimental Data ◽  
Energy Loss ◽  
Physical State ◽  
Empirical Equation ◽  
Electronic Energy ◽  
Fission Fragments ◽  
Fitting Procedure ◽  
Wide Range ◽  
Energy Degradation ◽  
Semi Empirical

A semi-empirical equation for the electronic energy loss of fission fragments has been derived by fitting the theoretical approach of Bohr, specifically developed for heavy stopping materials, to experimental data in gases and solids in a wide range of atomic numbers. The fitting procedure was performed by choosing a different expression for the number of electrons of the medium taking part in the stopping process, which includes empirical parameters obtained by fitting to experiment.The equation enables the energy loss of fission fragments in substances of any Z2, regardless of their physical state, to be predicted to a good degree of accuracy down to energies of approximately 20 MeV.

Mass Transfer in Liquid in an Apparatus with Mobile Packing. Application of a Dispersion Model

1993 ◽  
Vol 58 (5) ◽  
pp. 1078-1086
Author(s):  
Zdeněk Palatý
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Empirical Equation ◽  
Dispersion Model ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients

The paper deals with the mass transfer in a liquid on a plate with mobile packing. A procedure has been suggested which enables estimation of the mass transfer coefficients from experimental data considering the dispersion flow of the liquid. The results obtained from the desorption of CO2 from water are presented graphically and in the form of empirical equation.

scholarly journals Correlation between Buoyancy Flux, Dissipation and Potential Vorticity in Rotating Stratified Turbulence

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 157
Author(s):  
Duane Rosenberg ◽  
Annick Pouquet ◽  
Raffaele Marino
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Potential Vorticity ◽  
Isotropic Turbulence ◽  
Joint Probability ◽  
Buoyancy Flux ◽  
Turbulent Regime ◽  
Stratified Turbulence ◽  
Low Dissipation ◽  
Linear And Nonlinear

We study in this paper the correlation between the buoyancy flux, the efficiency of energy dissipation and the linear and nonlinear components of potential vorticity, PV, a point-wise invariant of the Boussinesq equations, contrasting the three identified regimes of rotating stratified turbulence, namely wave-dominated, wave–eddy interactions and eddy-dominated. After recalling some of the main novel features of these flows compared to homogeneous isotropic turbulence, we specifically analyze three direct numerical simulations in the absence of forcing and performed on grids of 10243 points, one in each of these physical regimes. We focus in particular on the link between the point-wise buoyancy flux and the amount of kinetic energy dissipation and of linear and nonlinear PV. For flows dominated by waves, we find that the highest joint probability is for minimal kinetic energy dissipation (compared to the buoyancy flux), low dissipation efficiency and low nonlinear PV, whereas for flows dominated by nonlinear eddies, the highest correlation between dissipation and buoyancy flux occurs for weak flux and high localized nonlinear PV. We also show that the nonlinear potential vorticity is strongly correlated with high dissipation efficiency in the turbulent regime, corresponding to intermittent events, as observed in the atmosphere and oceans.

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