scholarly journals MODEL SEBARAN SEDIMEN SUSPENSIMUARA SUNGAI SIAK RIAU

2013 ◽  
Vol 3 (2) ◽  
pp. 55-62
Author(s):  
Yeeri Badrun ◽  
Amin Ridhoni
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Mud Transport

Simulasi hidrodinamika aliran dan sedimen menggunakan modul yang terdapat dalam perangkat lunak MIKE21, yaitu Hydrodinamika Modul dan Mud Transport Modul. Model hidrodinamika tersebut merupakan model dengan metode elemen hingga dua dimensi horisontal dan rerata kedalaman. Dengan model numeris ini dapat diprediksi pola aliran, elevasi muka air dan komponen kecepatan horisontal baik pada kondisi aliran permanen (steady flow) maupun aliran tak permanen (unsteady flow) serta sedimentasi. Di dalam simulasi sebaran sedimen di muara Sungai Siak, dilakukan dalam 3 skenario input konsentrasi yaitu: skenario 1 dengan input konsentrasi 0,1 kg/ m3, skenario 2 dengan input konsentrasi 0,5 kg/ m3 dan skenario 3 dengan input konsentrasi 1 kg/ m3. Hasil simulasi pola arus disajikan dalam bentuk vektor dan kontur kecepatan serta dalam bentuk grafik. Secara visual kecepatan yang terjadi akibat terjadinya pasang surut adalah pada saat surut kecepatannya berkisar antara 0,20 m/detik sampai 0,34 m/detik dan saat pasang berkisar antara 0,01 m/detik sampai 0,02 m/detik. Pada saat pasang sebaran sedimen suspensi akan mengarah ke selatan dan pada saat surut sebaran sedimen suspensi cenderung ke arah utara. Perubahan elevasi dasar sungai akan meningkat secara signifikan dengan bertambahnya konsentrasi sedimen. Perubahan sangat terlihat jelas dari input konsentrasi 0,5 kg/ m3 ke 1 kg/m3 yaitu dari 0,036 cm/tahun menjadi 0,9 cm/tahun. Sedangkan pada dasar laut belum mengalami perubahan elevasi dasar karena konsentrasi sedimen terdifusi secara merata ke segala penjuru.

Experimental Study on the Piping Erosion Mechanism of Gap-Graded Soils Under a Supercritical Hydraulic Gradient

2021 ◽  
Author(s):  
Liang Chen ◽  
Yu Wan ◽  
Jian-Jian He ◽  
Chun-Mu Luo ◽  
Shu-fa Yan ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Unsteady Flow ◽  
Relative Density ◽  
Flow Velocity ◽  
Steady Flow ◽  
Fine Particle ◽  
Failure Process ◽  
Hydraulic Gradient ◽  
Particle Content ◽  
Piping Erosion

Abstract Seepage-induced piping erosion is observed in many geotechnical structures. This paper studies the piping mechanism of gap-graded soils during the whole piping erosion failure process under a supercritical hydraulic gradient. We define the supercritical ratio Ri and study the change in the parameters such as the flow velocity, hydraulic conductivity, and fine particle loss with Ri. Under steady flow, a formula for determining the flow velocity state of the sample with Ri according to the fine particle content and relative density of the sample was proposed; during the piping failure process, the influence of Rimax on the rate at which the flow velocity and hydraulic conductivity of the sample increase as Ri decreases was greater than that of the initial relative density and the initial fine particle content of the sample. Under unsteady flow, a larger initial relative density corresponds to a smaller amplitude of increase in the average value of the peak flow velocity with increasing Ri. Compared with the test under steady flow, the flow velocity under unsteady flow would experience abrupt changes. The relative position of the trend line L of the flow velocity varying with Ri under unsteady flow and the fixed peak water head height point A under steady flow were related to the relative density of the sample.

scholarly journals Experimental study on water level and absorption capacity in a radial well flow in a loess area

2018 ◽  
Vol 19 (5) ◽  
pp. 1313-1321
Author(s):  
Xuezhen Zhang ◽  
Aidi Huo ◽  
Jucui Wang
Keyword(s):  
Unsteady Flow ◽  
Water Absorption ◽  
Water Level ◽  
Steady Flow ◽  
Flow Injection ◽  
Absorption Capacity ◽  
Water Absorption Capacity ◽  
Analysis Method ◽  
Semi Empirical ◽  
Radial Well

Abstract In this paper, the theoretical basis for flow calculation in an injection well was discussed. It proposed that the flow rate of an injection well could be calculated referring to pumping theory and method. A mathematical model of the rising curve of water level around a radial well was established and the equation for calculating the rising curve was given. The calculation equations selected for the water absorption capacity of injection wells were explained and examples were verified and compared. The results indicated that, under the same injection conditions, the water level value calculated by the analysis method was slightly larger, but the error between the analysis method and the semi-theoretical and semi-empirical methods was small. In the processes of steady flow injection and unsteady flow injection, there was a small difference of water absorption capacity, and the former was slightly larger. The measured values of water absorption capacity were only about one-third of the calculated values based on pumping theory. Overall, the analytical solution method for predicting the rising curve of water level has priority in well injection. The semi-theoretical and semi-empirical equation for calculating water absorption capacity sifted first has priority in steady flow injection, the equation sifted second has priority in unsteady flow injection.

CFD Comparison of Steady and Unsteady Flow Through a Human Nasal Passage

2009 ◽  
Author(s):  
Brian Savilonis ◽  
Kalen Smith
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Flow Behavior ◽  
Flow Dynamics ◽  
Nasal Passage ◽  
Normal Breathing ◽  
Flow Through ◽  
Nasal Flow

Understanding of the transnasal pressure and flow behavior during normal breathing conditions has been a subject of much discussion and research. In particular we are interested in testing the hypothesis of quasi-steady flow as well as the role of turbulence on nasal flow dynamics.

Unsteady flow about a sphere at low to moderate Reynolds number. Part 1. Oscillatory motion

1994 ◽  
Vol 277 ◽  
pp. 347-379 ◽  
Author(s):  
Eugene J. Chang ◽  
Martin R. Maxey
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Steady Flow ◽  
Oscillatory Flow ◽  
Reynolds Numbers ◽  
Oscillatory Motion ◽  
Rigid Sphere ◽  
Flow Conditions ◽  
Steady Streaming ◽  
Moderate Reynolds Number

A direct numerical simulation, based on spectral methods, has been used to compute the time-dependent, axisymmetric viscous flow past a rigid sphere. An investigation has been made for oscillatory flow about a zero mean for different Reynolds numbers and frequencies. The simulation has been verified for steady flow conditions, and for unsteady flow there is excellent agreement with Stokes flow theory at very low Reynolds numbers. At moderate Reynolds numbers, around 20, there is good general agreement with available experimental data for oscillatory motion. Under steady flow conditions no separation occurs at Reynolds number below 20; however in an oscillatory flow a separation bubble forms on the decelerating portion of each cycle at Reynolds numbers well below this. As the flow accelerates again the bubble detaches and decays, while the formation of a new bubble is inhibited till the flow again decelerates. Steady streaming, observed for high frequencies, is also observed at low frequencies due to the flow separation. The contribution of the pressure to the resultant force on the sphere includes a component that is well described by the usual added-mass term even when there is separation. In a companion paper the flow characteristics for constant acceleration or deceleration are reported.

Numerical Simulation of the Viscous Flow for the Supersonic Jet Element

2011 ◽  
Vol 189-193 ◽  
pp. 2362-2365
Author(s):  
Yong Yu ◽  
Guo Qing Zhang ◽  
Fei Wang
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Unsteady Flow ◽  
Viscous Flow ◽  
Steady Flow ◽  
Supersonic Jet ◽  
Calculated Data ◽  
Numerical Precision ◽  
Good Agreement

The viscous flow of the supersonic jet element was simulated numerically based on CFD technology, and many tests have been done to verify the numerical precision. The results show that the calculated data are good agreement with the experimental data. So the numerical simulation of the viscous flow for the supersonic jet element is accurate and reliable, and it can be applied to investigate the steady flow and unsteady flow in supersonic jet element.

scholarly journals Deterministic Stress Modeling of Hot Gas Segregation in a Turbine

1999 ◽  
Author(s):  
Judy Busby ◽  
Doug Sondak ◽  
Brent Staubach ◽  
Roger Davis
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Three Dimensional ◽  
Design Tool ◽  
Source Terms ◽  
Flow Equations ◽  
Flow Solution ◽  
Viscous Solution ◽  
Hot Streak ◽  
Gas Segregation

Simulation of unsteady viscous turbomachinery flowfields is presently impractical as a design tool due to the long run times required. Designers rely predominantly on steady-state simulations, but these simulations do not account for some of the important unsteady flow physics. Unsteady flow effects can be modeled as source terms in the steady flow equations. These source terms, referred to as Lumped Deterministic Stresses (LDS), can be used to drive steady flow solution procedures to reproduce the time-average of an unsteady flow solution. The goal of this work is to investigate the feasibility of using inviscid lumped deterministic stresses to model unsteady combustion hot streak migretion effects on the turbine blade tip and outer air seal heat loads. The LDS model is obtained from an unsteady inviscid calculation. The inviscid LDS model is then used with a steady viscous computation to simulate the time-averaged viscous solution. The feasibility of the inviscid LDS model is demonstrated on a single stage, three-dimensional, vane-blade turbine with a hot streak entering the vane passage at mid-pitch and mid-span. The steady viscous solution with the LDS model is compared to the time-averaged viscous, steady viscous and time-averaged inviscid computations. The LDS model reproduces the time-averaged viscous temperature distribution on the outer air seal to within 2.3%, while the steady viscous has an error of 8.4%, and the time-averaged inviscid calculation has an error of 17.2%. The solution using the LDS model is obtained at a cost in CPU time that is 26% of that required for a time-averaged viscous computation.

Aeroelasticity at Reversed Flow Conditions: Part 1—Numerical and Experimental Investigations of a Compressor Cascade With Controlled Vibration

2011 ◽  
Author(s):  
Harald Schoenenborn ◽  
Virginie Chenaux ◽  
Peter Ott
Keyword(s):  
Steady State ◽  
Flow Field ◽  
Unsteady Flow ◽  
Steady Flow ◽  
Experimental Investigations ◽  
Blade Surface ◽  
Flow Conditions ◽  
Steady State Flow ◽  
Reversed Flow ◽  
Blow Down

The prediction of flutter and forced response at normal flow conditions has become a standard procedure during the design of compressor airfoils. But at severe off-design conditions, the flow field becomes very complex, especially during the surge blow-down phase where reversed flow conditions occur. The correct prediction of the unsteady pressures and the resulting aerodynamic excitation or damping at these conditions remains an extremely challenging task. In the first part of the paper, basic investigations for these flow conditions are presented. Aeroelastic calculations during compressor surge are shown in the second part. Experimental investigations were performed in the Annular Test Facility for non-rotating cascades at EPF Lausanne. The test cascade was exposed to flow conditions as expected during the surge blow-down phase which is characterized by large separation regions. Measurements of the steady-state flow conditions on the blade surface, at the outer wall, upstream and downstream of the cascade provided detailed information about the steady flow conditions. The cascade was then subjected to controlled vibration of the blades with constant amplitudes and inter-blade phase angles. Unsteady pressure measurements on the blade surface and at the casing wall provided information about the resulting unsteady flow conditions. Analytical CFD calculations were performed. The steady flow field was calculated using a RANS code. Based on the steady-state flow field, unsteady calculations applying a linearized code were carried out. The agreement between measurements and calculations shows that the steady flow as well as the unsteady flow phenomena can be predicted quantitatively. In addition, knowing the blade vibration mode shape, which in this case is a torsion mode, the aerodynamic damping can be determined for the corresponding flow conditions.

Unsteady Vortex Breakdown Phenomena in an Enclosed Cylindrical Container With a Rotating Endwall Disk

2019 ◽  
Author(s):  
Yuki Nakatsuka ◽  
Reima Iwatsu ◽  
Jae Min Hyun ◽  
Hide S. Koyama
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Vortex Breakdown ◽  
Polar Angle ◽  
Injection Technique ◽  
Cylindrical Container ◽  
Stagnation Points ◽  
Axial Oscillation ◽  
Time Period ◽  
Dimensional Parameters

Abstract A high-quality precision-controlled turntable apparatus was fabricated to probe the dynamic behavior of a viscous fluid contained in a cylindrical container. Vortex breakdown(s) produced by a rotating endwall disk was visualized by using a fluorescent dye injection technique, and its flow field was measured by using a particle image velocimetry. This flow is characterized by two non-dimensional parameters, i.e., the height-to-radius ratio H/R and the rotating Reynolds number Re = Ω2/v. Limiting boundaries for single, double and triple vortex breakdowns in steady flow were re-plotted to compare with the previous visualization studies of Escudier. The locations of stagnation points of the vortex breakdown bubble(s) in steady flow were measured quantitatively. The overall experimental results in the steady flow were in excellent agreement with Escudier’s data. In unsteady flow, the amplitude and time period of periodic axial oscillation, and the polar angle and time period of precession, were measured. The domains for periodic axial oscillation and for precession in unsteady flow were delineated.

Numerical Simulation of Wave Energy Converter With Hydrofoil Blades Under Various Wave Conditions

2019 ◽  
Author(s):  
Jie Lei ◽  
Erasmo Gonzalez ◽  
Yingchen Yang ◽  
Ying Zhang ◽  
Ben Xu
Keyword(s):  
Unsteady Flow ◽  
Energy Conversion ◽  
Steady Flow ◽  
Conversion Efficiency ◽  
Wave Energy ◽  
Rotational Speed ◽  
Rotational Velocity ◽  
Ocean Waves ◽  
Energy Conversion Efficiency ◽  
Wave Conditions

Abstract Ocean wave is a rich source of renewable energy with much higher power density than winds. Various WEC technologies have been proposed or are under development. In this study, we developed a 2-dimensional (2D) model and analyzed the rotational motion of the lift-type rotor’s blade under steady flow and unsteady flow. The numerical model was validated by experiments under steady flow. Fast Fourier Transform (FFT) analysis was performed to identify the major contribution of frequency in terms of vortexes generated in the flow field. A comparative study was also performed by comparing all the cases in terms of energy conversion efficiency under different wave conditions. It turns out that the efficiency of energy conversion has a maximum value in the steady flow, while the efficiency for unsteady flow keeps decreasing, therefore this is highly due to the increased dissipation because of the oscillating. When the flow is oscillating, the rotational speed of the rotor under periodic condition is lower than the rotational velocity with steady flow, and a curve fitting was performed in this study to predict the periodic average rotational speed. We conclude that for oscillating flow a minimum of 1.6% energy conversion efficiency can be expected, but it may vary for the actual ocean waves. It is expected the current 2D simulation results can contribute to the wave energy community, especially when the rotor design and optimization is required.

Analysis of Fully Developed Unsteady Viscous Flow in a Curved Elastic Tube Model to Provide Fluid Mechanical Data for Some Circulatory Path-Physiological Situations and Assist Devices

1979 ◽  
Vol 101 (2) ◽  
pp. 114-123 ◽  
Author(s):  
K. B. Chandran ◽  
R. R. Hosey ◽  
D. N. Ghista ◽  
V. W. Vayo
Keyword(s):  
Shear Stress ◽  
Unsteady Flow ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Flow Patterns ◽  
Elastic Tube ◽  
Flow Component ◽  
Flow Response ◽  
Elastic Tubes ◽  
Flow Components

The unsteady and steady flow components of pulsatile flow response, to an experimentally monitored representative pressure pulse, are computed to provide fluid mechanical data for the etiology of arteriosclerosis at arterial curvature sites and for the design analysis of some extracorporeal dialysis and oxygenatory systems. The unsteady flow component of pulsatile flow in curved elastic tubes is simulated by the superposition of the first six Fourier components of a derived oscillatory flow solution of a viscous, incompressible fluid through an elastic tube of small curvature. The computer flow patterns, wall shear stress and hoop and axial stresses in the wall, due to unsteady and steady flow components of pulsatile flow response, are compared and their implications are discussed. The results show that the unsteady component yields shear stress of an order of magnitude greater than the steady flow, but the steady flow component has a greater variation in the shear stress distribution over a cross section. The steady and unsteady flow patterns are presented for several values of the tube diameters and curvature parameters typical of major arteries in the human circulatory system. The flow pattern and the stress variations could also prove useful in the design of extracorporeal systems such as dialysis machines and oxygenators.

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