scholarly journals Effects of morphology in controlling propagation of density currents in a reservoir using uncalibrated three-dimensional hydrodynamic modeling

2020 ◽  
Author(s):  
Behnam Zamani ◽  
Manfred Koch ◽  
Ben R. Hodges
Keyword(s):  
Hydrodynamic Model ◽  
Large Scale ◽  
Three Dimensional ◽  
Density Current ◽  
Density Currents ◽  
Large Reservoir ◽  
Bottom Water Temperature ◽  
The Difference ◽  
Basin Morphology ◽  
Southwest Iran

In this study, effects of basin morphology are shown to affect density current hydrodynamics of a large reservoir using a three-dimensional (3D) hydrodynamic model that is validated (but not calibrated) with in situ observational data. The AEM3D hydrodynamic model was applied for 5-month simulations during winter and spring flooding for the Maroon reservoir in southwest Iran, where available observations indicated that large-scale density currents had previously occurred. The model results were validated with near-bottom water temperature measurements that were previously collected at five locations in the reservoir. The Maroon reservoir consists of upper and lower basins that are connected by a deep and narrow canyon. Analyses of simulations show that the canyon strongly affects density current propagation and the resulting differing limnological characteristics of the two basins. The evolution of the Wedderburn Number, Lake Number, and Schmidt stability number are shown to be different in the two basins, and the difference is attributable to the morphological separation by the canyon. Investigation of the background potential energy (BPE) changes along the length of the canyon indicated that a density front passes through the upper section of the canyon but is smoothed into simple filling of the lower basin. The separable dynamics of the basins has implications for the complexity of models needed for representing both water quality and sedimentation.

Three-Dimensional Structures in Experimental Density Currents

2007 ◽  
Author(s):  
B. Firoozabadi ◽  
H. Afshin ◽  
E. Safaaee
Keyword(s):  
Salt Solution ◽  
Chemical Elements ◽  
Three Dimensional ◽  
Lateral Spreading ◽  
Current Data ◽  
Density Current ◽  
Density Currents ◽  
Ambient Water ◽  
Data Set ◽  
Bed Slope

Density currents are continuous currents which move down-slope due to the fact that their density is greater than that of ambient water. The density difference is caused by temperature differences, chemical elements, dissolved materials, or suspended sediment. Many researchers have studied the density current structures, their complexities and uncertainties. However, there is not a detailed 3-D turbulent density current data set perfectly. In this work, the structure of 3-dimensional salt solution density currents is investigated. A laboratory channel was used to study the flow resulting from the release of salt solution into freshwater over an inclined bed. The experiments were conducted with different bottom slopes, inlet concentrations and flow rates. In these tests, the instantaneous velocities are measured by an ADV apparatus (Acoustic Doppler Velocimeter). Results show that by increasing the bed-slope and inlet concentrations, the height of the current decreases. As the density current moves downward the channel or by increasing the discharge, the height of the density current increases. Finally, the effects of different variables such as the bed slope, concentration and flow rate of entering fluid on the velocity profile in different distances from the entrance is studied. The entrainment coefficient, lateral spreading and drag coefficient of the bed and shear layer between salt solution and ambient water is discussed.

Experimental Investigation of Turbulence Specifications of 3-D Density Currents

2007 ◽  
Author(s):  
B. Firoozabadi ◽  
H. Afshin ◽  
A. Baghaer Poor
Keyword(s):  
Experimental Investigation ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Turbulence Energy ◽  
Density Current ◽  
Turbulence Characteristic ◽  
Acoustic Doppler Velocimeter ◽  
Density Currents ◽  
Flow Rates

The present study investigates the turbulence characteristic of density current experimentally. The 3D Acoustic-Doppler Velocimeter (ADV) was used to measure the instantaneous velocity and characteristics of the turbulent flow. The courses of experiment were conducted in a three-dimensional channel for different discharge flows, concentrations, and bed slopes. Results are expressed at various distances from the inlet, for all flow rates, slopes and concentrations as the distribution of turbulence energy, Reynolds stress and the turbulent intensity. It was concluded that the maximum turbulence intensity happens in both the interface and near the wall. Also it was observed that turbulence intensity reaches its minimum where maximum velocity occurs.

EXPERIMENTS ON DENSITY AND TURBIDITY CURRENTS: II. UNIFORM FLOW OF DENSITY CURRENTS

1966 ◽  
Vol 3 (5) ◽  
pp. 627-637 ◽  
Author(s):  
Gerard V. Middleton
Keyword(s):  
Reynolds Number ◽  
Average Velocity ◽  
Large Scale ◽  
Quantitative Estimation ◽  
Uniform Flow ◽  
Turbidity Currents ◽  
Density Current ◽  
Density Currents ◽  
Review Of The Literature ◽  
Fluid Interface

The basic theory for the average velocity of uniform flow of a density current is now well established. The resistance at the bottom may be estimated from reasonable assumptions regarding the roughness of the bottom and the size of the current. The principal problem remaining is quantitative estimation of the resistance of the upper (fluid) interface. A review of the literature suggests that this resistance increases with increase in Froude number and decreases with increase in Reynolds number, and the writer's experiments support this hypothesis.As many turbidity currents are large scale and flow over low slopes of relatively small roughness it seems probable that both the bottom resistance and the resistance at the upper interface are small.

scholarly journals Determination of Some Body Measurements of Camels With Three Dimensional Modeling Method (3D)

2021 ◽  
Author(s):  
Alkan çağlı ◽  
M. Yılmaz
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Practical Method ◽  
Modeling Method ◽  
The Body ◽  
Body Measurements ◽  
3D Measurement ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
The Difference

Abstract In this study, the use of three-dimensional modeling method was tested in taking some body measurements in camels with a practical method and was compared with other measurement methods. As the animal material of the study, 12 single humped dromedary female camels and 14 double humped Camelus dromedarius X Camelus bactrianus: F1 male camels, totally 26 camels, were used in three camel farms in Incirliova district of Aydın province. The body measurements taken from each animal by using different three methods, namely by Manuel Method (MM), by Photography Method (PM), and by Three Dimensional Modeling Method (3D) were the Cidago Height (CH), the Back Height (BH), the Rump Height (RH), the Body Length (BL), the Brisket Height (BRH), the Abdominal Height (AH), the Shoulder Width (SW) and the Rump Width (RW) and these values were compared with each other. As a result of this study, the mean values of MM and 3D measurement values were very close to each other and the difference between them was found to be statistically insignificant. (P<0.05). The difference between the means of PM and MM/3D measurement values was found to be significant. (P <0.05). In the measurements taken by MM, 3D, PM methods in male camels, the values obtained by MM and 3D methods for CH, BH, RH, BRH, AH, BL, and SW were very close to each other and the differences between them were found insignificant statistically (p < 0.05). On the determined regression graph, a linear was found between MM and 3D measurement values. As a result of this study, it has been determined that the 3D modeling method can be used as a remote and more practical method in determining the morphological features of large-scale animals such as camels more reliably, more easily and more practically.

3-D Simulation of Conservative and Non-Conservative Density Current

2006 ◽  
Author(s):  
S. Hormozi ◽  
B. Firoozabadi ◽  
H. Ghasvari Jahromi ◽  
S. M. H. Moosavi Hekmati
Keyword(s):  
Flow Structure ◽  
Environmental Flows ◽  
Three Dimensional ◽  
Turbidity Currents ◽  
Density Current ◽  
Density Currents ◽  
Straight Channel ◽  
Suspended Material ◽  
Series Of Experiments ◽  
Good Agreement

Flows generated by density differences are called gravity or density currents which are generic features of many environmental flows. These currents are classified as the conservative and non-conservative flows whether the buoyancy flux is conserved or changed respectively. In this paper, a low Reynolds k-ε turbulence model is used to simulate three dimensional density and turbidity currents. Also, a series of experiments were conducted in a straight channel to study the characteristics of the non-conservative density current. In experiments, Kaolin was used as the suspended material. Comparisons are made between conservative and non-conservative's height, concentration and velocity profiles of the current and their variations along the transverse intersections. Outcomes indicate that the presence of the particles influences the flow structure sensibly. The results are compared with the experiments and showed a good agreement.

Direct Numerical Simulations of Planar and Cylindrical Density Currents

2005 ◽  
Vol 73 (6) ◽  
pp. 923-930 ◽  
Author(s):  
Mariano I. Cantero ◽  
S. Balachandar ◽  
Marcelo H. García ◽  
James P. Ferry
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Boussinesq Approximation ◽  
The Body ◽  
Density Current ◽  
Density Currents ◽  
Mean Flow ◽  
Viscous Effects ◽  
Spreading Velocity ◽  
Slip Boundary

The collapse of a heavy fluid column in a lighter environment is studied by direct numerical simulation of the Navier-Stokes equations using the Boussinesq approximation for small density difference. Such phenomenon occurs in many engineering and environmental problems resulting in a density current spreading over a no-slip boundary. In this work, density currents corresponding to two Grashof (Gr) numbers are investigated (105 and 1.5×106) for two very different geometrical configurations, namely, planar and cylindrical, with the goal of identifying differences and similarities in the flow structure and dynamics. The numerical model is capable of reproducing most of the two- and three-dimensional flow structures previously observed in the laboratory and in the field. Soon after the release of the heavier fluid into the quiescent environment, a density current forms exhibiting a well-defined head with a hanging nose followed by a shallower body and tail. In the case of large Gr, the flow evolves in a three-dimensional fashion featuring a pattern of lobes and clefts in the intruding front and substantial three-dimensionality in the trailing body. For the case of the lower Gr, the flow is completely two dimensional. The dynamics of the current is visualized and explained in terms of the mean flow for different phases of spreading. The initial phase, known as slumping phase, is characterized by a nearly constant spreading velocity and strong vortex shedding from the front of the current. Our numerical results show that this spreading velocity is influenced by Gr as well as the geometrical configuration. The slumping phase is followed by a decelerating phase in which the vortices move into the body of the current, pair, stretch and decay as viscous effects become important. The simulated dynamics of the flow during this phase is in very good agreement with previously reported experiments.

scholarly journals The Intrusion Depth of Density Currents Flowing into Stratified Water Bodies

2009 ◽  
Vol 39 (8) ◽  
pp. 1935-1947 ◽  
Author(s):  
Mathew Wells ◽  
Parthiban Nadarajah
Keyword(s):  
Water Column ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Buoyancy Flux ◽  
Density Current ◽  
Density Currents ◽  
Coriolis Parameter ◽  
Entrainment Ratio ◽  
Geostrophic Balance ◽  
Intrusion Depth

Abstract Theory and laboratory experiments are presented describing the depth at which a density current intrudes into a linearly stratified water column, as a function of the entrainment ratio E, the buoyancy flux in the dense current B, and the magnitude of the stratification N. The main result is that Z ∼ E−1/3B1/3/N. It is shown that the depth of the intrusion scales as Z ∼ (3 ± 1)B1/3/N for laboratory experiments, and as for oceanic density currents. The velocity of a large-scale density current is controlled by a geostrophic balance defined as Ugeo = 0.25g′s/f, where s is the slope and f is the Coriolis parameter. The geostrophic buoyancy flux is then defined by Bgeo = g′Ugeoh, with g′ the reduced gravity and h the thickness of the current. The scaling herein implies that the depth of an oceanic intrusion is relatively insensitive to changes in source water properties but is very sensitive to changes in the stratification of the water column, consistent with the previous scaling of Price and Baringer. For example, if the buoyancy flux of a dense current were to double while the stratification remained constant, then there would only be a 25% increase in the intrusion depth, whereas doubling the stratification would result in a 50% decrease of the intrusion depth.

Kármán–Howarth solutions of homogeneous isotropic turbulence

2021 ◽  
Vol 932 ◽  
Author(s):  
L. Djenidi ◽  
R.A. Antonia
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Three Dimensional ◽  
Order Moment ◽  
Homogeneous Isotropic Turbulence ◽  
The Difference ◽  
Decaying Turbulence ◽  
The Impact ◽  
Good Agreement

The Kármán–Howarth equation (KHEq) is solved using a closure model to obtain solutions of the second-order moment of the velocity increment, $S_2$ , in homogeneous isotropic turbulence (HIT). The results are in good agreement with experimental data for decaying turbulence and are also consistent with calculations based on the three-dimensional energy spectrum for decaying HIT. They differ, however, from those for forced HIT, the difference occurring mainly at large scales. This difference is attributed to the fact that the forcing generates large-scale motions which are not compatible with the KHEq. As the Reynolds number increases, the impact of forcing on the small scales decreases, thus allowing the KHEq and spectrally based solutions to agree well in the range of scales unaffected by forcing. Finally, the results show that the two-thirds law is compatible with the KHEq solutions as the Reynolds number increases to very large, if not infinite, values.

EXPERIMENTS ON DENSITY AND TURBIDITY CURRENTS: I. MOTION OF THE HEAD

1966 ◽  
Vol 3 (4) ◽  
pp. 523-546 ◽  
Author(s):  
Gerard V. Middleton
Keyword(s):  
Turbidity Current ◽  
Turbidity Currents ◽  
Density Current ◽  
Density Currents ◽  
Salt Solutions ◽  
Overlying Water ◽  
Numerical Coefficient ◽  
Series Of Experiments ◽  
The Difference ◽  
Clay Suspensions

Two series of experiments were performed in a lucite flume 5 meters long, 50 cm deep, and 15.4 cm wide. In the first series saline density currents were formed by pumping salt solutions at constant discharge into the tilted flume. In the second series, the flume was horizontal and turbidity currents were formed by the releasing of suspensions of plastic beads from a box at one end.In both series of experiments a characteristic head was formed at the front of the flow. It was found that the motion of the head in the turbidity current experiments was closely described by laws developed by Keulegan (1958) for saline surges, and it is concluded that certain aspects of the motion of turbidity current heads can be investigated indirectly by means of experiments on density currents formed from clay suspensions or salt solutions.The salt-solution experiments were designed to investigate the effect of bottom slope on the motion of density current heads. It was found that the velocity of density (and by inference, turbidity) current heads on slopes up to 4% is adequately expressed by Keulegan's formula[Formula: see text]where v is the velocity of the head, Δρ is the difference between the density of the current (ρ) and that of the overlying water, d2 is the thickness of the head, and g is the acceleration due to gravity. The numerical coefficient is approximately constant, but may increase slightly with increase in slope. The form of the equation differs greatly from that of the Chézy equation which has previously been used for the analysis of the movement of turbidity currents.Observations were also made regarding the shape of the head and the motion within and in front of the head.

scholarly journals Stability of three-dimensional columnar convection in a porous medium

2017 ◽  
Vol 829 ◽  
pp. 89-111 ◽  
Author(s):  
Duncan R. Hewitt ◽  
John R. Lister
Keyword(s):  
Porous Medium ◽  
Aspect Ratio ◽  
Large Scale ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Base Flow ◽  
Apparent Difference ◽  
Exchange Flow ◽  
Two Dimensional ◽  
The Difference

The stability of steady convective exchange flow with a rectangular planform in an unbounded three-dimensional porous medium is explored. The base flow comprises a balance between vertical advection with amplitude $A$ in interleaving rectangular columns with aspect ratio $\unicode[STIX]{x1D709}\leqslant 1$ and horizontal diffusion between the columns. Columnar flow with a square planform ($\unicode[STIX]{x1D709}=1$) is found to be weakly unstable to a large-scale perturbation of the background temperature gradient, irrespective of $A$, but to have no stronger instability on the scale of the columns. This result provides a stark contrast to two-dimensional columnar flow (Hewitt et al., J. Fluid Mech., vol. 737, 2013, pp. 205–231), which, as $A$ is increased, is increasingly unstable to a perturbation on the scale of the columnar wavelength. For rectangular planforms with $\unicode[STIX]{x1D709}<1$, a critical aspect ratio is identified, below which a perturbation on the scale of the columns is the fastest growing mode, as in two dimensions. Scalings for the growth rate and the structure of this mode are identified, and are explained by means of an asymptotic expansion in the limit $\unicode[STIX]{x1D709}\rightarrow 0$. The difference between the stabilities of two-dimensional and three-dimensional exchange flow provides a potential explanation for the apparent difference in dominant horizontal scale observed in direct numerical simulations of two-dimensional and three-dimensional statistically steady ‘Rayleigh–Darcy’ convection at high Rayleigh numbers.

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