scholarly journals A spectral multidomain penalty method solver for the numerical simulation of granular avalanches

2019 ◽  
Vol 23 (4) ◽  
pp. 317-329
Author(s):  
Mario Germán Trujillo-Vela ◽  
Jorge Alberto Escobar-Vargas ◽  
Alfonso Mariano Ramos-Cañón
Keyword(s):  
Numerical Simulation ◽  
Granular Flow ◽  
Penalty Method ◽  
Earth Pressure ◽  
Small Scale ◽  
Flow Equations ◽  
Numerical Predictions ◽  
Lateral Earth Pressure ◽  
High Order Element ◽  
Granular Avalanche

This work presents a high-order element-based numerical simulation of an experimental granular avalanche, in order to assess the potential of these spectral techniques to handle conservation laws in geophysics. The spatial discretization of these equations was developed via the spectral multidomain penalty method (SMPM). The temporal terms were discretized using a strong-stability preserving Runge-Kutta method. Stability of the numerical scheme is ensured with the use of a spectral filter and a constant or regularized lateral earth pressure coefficient. The test case is a granular avalanche that is generated in a small-scale rectangular flume with topographical gradient. A grid independence test was performed to clarify the order of the error in the mass conservation produced by the treatments here implemented. The numerical predictions of the granular avalanches are compared with experimental measurements performed by Denlinger & Iverson (2001). Furthermore, the boundary conditions and parameters such as lateral earth pressure coefficients and the momentum correction factor were analyzed to observe the incidence of these features when solving the granular flow equations. This work identifies the benefits and weaknesses of the SMPM to solve this set of equations and, it is possible to conclude that the SMPM provides an appropriate solution of the granular flow equations proposed by Iverson & Denlinger (2001). Besides, it produces comparable predictions to experimental data and numerical results given by other schemes.

Numerical Simulation on the Stress Characteristics of Prestressed Retaining Wall

2013 ◽  
Vol 477-478 ◽  
pp. 596-599
Author(s):  
Jian Qing Wu ◽  
Hong Bo Zhang ◽  
Xiu Guang Song ◽  
Yi Fan Yu ◽  
Chao Li
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Bearing Capacity ◽  
Retaining Wall ◽  
Earth Pressure ◽  
Lateral Earth Pressure ◽  
Prestressed Anchor

With the highway subgrade fill increasing, traditional retaining wall cannot meet the requirements for supporting. To meet this requirement, the prestressed opposite-pull retaining wall was put forward. Due to the anchor pull of the new-style retaining wall, its bearing capacity was enhanced, but the stress is not clear. In order to reveal the stress distribution of the prestressed opposite-pull retaining wall, FLAC3D was adept to do numerical simulation on the new-style retaining wall. It simulated three conditions of the wall with no anchor, with anchor but without prestress and with prestressed anchor. The results showed that, after the layout of prestressed anchor, the lateral earth pressure of the region near the anchor increased with the increase of prestress, the lateral earth pressure of the wall is parabola distribution. The lateral earth pressure was larger than that of the wall with no anchor and with anchor but without prestress. The bearing capacity of the retaining wall was effectively improved.

Numerical Study of the Pressure Drop in a Flame Arrestor Using a Porous Media Model

2020 ◽  
Author(s):  
Hoden A. Farah ◽  
Frank K. Lu ◽  
Jim L. Griffin
Keyword(s):  
Numerical Simulation ◽  
Porous Media ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Small Scale ◽  
Forchheimer Equation ◽  
Flow Equations ◽  
Numerical Studies ◽  
Porous Media Model ◽  
Empirical Coefficients

Abstract A numerical study of the flow characteristics of a crimped flame arrestor element was conducted using a porous media model. The porous zone was modeled using the Forchheimer equation. The Forchheimer equation was incorporated into the governing conservation equations as a momentum sink. A small-scale crimped flame arrestor element was tested to determine the empirical coefficients in the Forchheimer equation. The numerical simulation result using this porous media model was verified using experimental data. The flow characteristics of a four-inch detonation flame arrestor with the same crimp design as the small-scale sample, was simulated using the porous media model. The numerical simulation flow data were compared against experimental values and agreed to within five percent. The method used to determine the Forchheimer coefficients and the experimental test setup are described in detail. The application of the Forchheimer equation into the governing flow equations is presented. The challenges and limitation of numerical studies in flame arrestors applications are discussed. The simplification gained by using the porous media model in flame arrestor numerical studies is presented.

Study on Lateral Earth Pressure of Anchored Retaining Wall

2013 ◽  
Vol 353-356 ◽  
pp. 312-317
Author(s):  
Ying Yong Li ◽  
Li Zhi Zheng ◽  
Hong Bo Zhang ◽  
Xiu Guang Song ◽  
Zhi Chao Xue
Keyword(s):  
Numerical Simulation ◽  
Pressure Distribution ◽  
Model Test ◽  
Retaining Wall ◽  
Field Tests ◽  
Earth Pressure ◽  
Soil Pressure ◽  
Gravity Retaining Wall ◽  
Lateral Earth Pressure ◽  
The Stability

In order to ensure the security of gravity retaining wall in the high fill subgrade, the design of gravity retaining wall with anchors is proposed,the characteristic of the new wall is that comment anchors are added to the traditional gravity retaining wall,by friction anchors provide lateral pull to the wall so the stability of the new wall is improved. Because of the constraints of anchors, the lateral free deformation is influenced and the soil pressure distribution is very complicated, field tests showed that soil pressure distribution is nonlinear and pressure concentrate in anchoring position. In order to reveal the supporting mechanism of retaining wall and propose the soil pressure formula, the model test of anchor retaining wall is made and numerical simulation is done. The results show that soil pressure appears incresent above the anchor and decreasing below the anchor, the soil pressre also grew larger away from the anchor proximal in the horizontal direction.

scholarly journals Stress level effect on mobility of dry granular flows of angular rock fragments

Landslides ◽  
2021 ◽  
Author(s):  
B. Cagnoli
Keyword(s):  
Stress Level ◽  
Granular Flow ◽  
High Stress ◽  
Granular Flows ◽  
Flow Dynamics ◽  
Small Scale ◽  
Flow Volume ◽  
Rock Fragments ◽  
Rock Avalanches ◽  
Flow Mobility

AbstractGranular flows of angular rock fragments such as rock avalanches and dense pyroclastic flows are simulated numerically by means of the discrete element method. Since large-scale flows generate stresses that are larger than those generated by small-scale flows, the purpose of these simulations is to understand the effect that the stress level has on flow mobility. The results show that granular flows that slide en mass have a flow mobility that is not influenced by the stress level. On the contrary, the stress level governs flow mobility when granular flow dynamics is affected by clast agitation and collisions. This second case occurs on a relatively rougher subsurface where an increase of the stress level causes an increase of flow mobility. The results show also that as the stress level increases, the effect that an increase of flow volume has on flow mobility switches sign from causing a decrease of mobility at low stress level to causing an increase of mobility at high stress level. This latter volume effect corresponds to the famous Heim’s mobility increase with the increase of the volume of large rock avalanches detected so far only in the field and for this reason considered inexplicable without resorting to extraordinary mechanisms. Granular flow dynamics is described in terms of dimensionless scaling parameters in three different granular flow regimes. This paper illustrates for each regime the functional relationship of flow mobility with stress level, flow volume, grain size, channel width, and basal friction.

Direct numerical simulation of a turbulent jet impinging on a heated wall

2015 ◽  
Vol 764 ◽  
pp. 362-394 ◽  
Author(s):  
T. Dairay ◽  
V. Fortuné ◽  
E. Lamballais ◽  
L.-E. Brizzi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Nusselt Number ◽  
Direct Numerical Simulation ◽  
Temperature Fields ◽  
Heated Wall ◽  
Small Scale ◽  
Turbulent Regime ◽  
High Heat Transfer ◽  
Radial Evolution

AbstractDirect numerical simulation (DNS) of an impinging jet flow with a nozzle-to-plate distance of two jet diameters and a Reynolds number of 10 000 is carried out at high spatial resolution using high-order numerical methods. The flow configuration is designed to enable the development of a fully turbulent regime with the appearance of a well-marked secondary maximum in the radial distribution of the mean heat transfer. The velocity and temperature statistics are validated with documented experiments. The DNS database is then analysed focusing on the role of unsteady processes to explain the spatial distribution of the heat transfer coefficient at the wall. A phenomenological scenario is proposed on the basis of instantaneous flow visualisations in order to explain the non-monotonic radial evolution of the Nusselt number in the stagnation region. This scenario is then assessed by analysing the wall temperature and the wall shear stress distributions and also through the use of conditional averaging of velocity and temperature fields. On one hand, the heat transfer is primarily driven by the large-scale toroidal primary and secondary vortices emitted periodically. On the other hand, these vortices are subjected to azimuthal distortions associated with the production of radially elongated structures at small scale. These distortions are responsible for the appearance of very high heat transfer zones organised as cold fluid spots on the heated wall. These cold spots are shaped by the radial structures through a filament propagation of the heat transfer. The analysis of probability density functions shows that these strong events are highly intermittent in time and space while contributing essentially to the secondary peak observed in the radial evolution of the Nusselt number.

Feedback Control of Turbulence

1994 ◽  
Vol 47 (6S) ◽  
pp. S3-S13 ◽  
Author(s):  
Parviz Moin ◽  
Thomas Bewley
Keyword(s):  
Feedback Control ◽  
Turbulent Flows ◽  
Systems Approach ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Small Scale ◽  
Flow Equations ◽  
Active Feedback ◽  
Active Feedback Control ◽  
Mathematical Techniques

A brief review of current approaches to active feedback control of the fluctuations arising in turbulent flows is presented, emphasizing the mathematical techniques involved. Active feedback control schemes are categorized and compared by examining the extent to which they are based on the governing flow equations. These schemes are broken down into the following categories: adaptive schemes, schemes based on heuristic physical arguments, schemes based on a dynamical systems approach, and schemes based on optimal control theory applied directly to the Navier-Stokes equations. Recent advances in methods of implementing small scale flow control ideas are also reviewed.

scholarly journals Computation of Three-Dimensional, Rotational Flow Through Turbomachinery Blade Rows for Improved Aerodynamic Design Studies

1986 ◽  
Author(s):  
S. V. Subramanian ◽  
R. Bozzola ◽  
Louis A. Povinelli
Keyword(s):  
Three Dimensional ◽  
Maximum Flow ◽  
Cost Effective ◽  
Computer Code ◽  
Integration Scheme ◽  
Aerodynamic Design ◽  
Design Studies ◽  
Flow Equations ◽  
Transonic Compressor ◽  
Numerical Predictions

The performance of a three dimensional computer code developed for predicting the flowfield in stationary and rotating turbomachinery blade rows is described in this study. The four stage Runge-Kutta numerical integration scheme is used for solving the governing flow equations and yields solution to the full, three dimensional, unsteady Euler equations in cylindrical coordinates. This method is fully explicit and uses the finite volume, time marching procedure. In order to demonstrate the accuracy and efficiency of the code, steady solutions were obtained for several cascade geometries under widely varying flow conditions. Computed flowfield results are presented for a fully subsonic turbine stator and a low aspect ratio, transonic compressor rotor blade under maximum flow and peak efficiency design conditions. Comparisons with Laser Anemometer measurements and other numerical predictions are also provided to illustrate that the present method predicts important flow features with good accuracy and can be used for cost effective aerodynamic design studies.

Experimental and Numerical Evaluation of Small-Scale Cryosurgery Using Ultrafine Cryoprobe

2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Junnosuke Okajima ◽  
Atsuki Komiya ◽  
Shigenao Maruyama
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Numerical Evaluation ◽  
Small Scale ◽  
Outer Diameter ◽  
Cooling Performance ◽  
The Heat Transfer Coefficient

The objective of this work is to experimentally and numerically evaluate small-scale cryosurgery using an ultrafine cryoprobe. The outer diameter (OD) of the cryoprobe was 550 μm. The cooling performance of the cryoprobe was tested with a freezing experiment using hydrogel at 37 °C. As a result of 1 min of cooling, the surface temperature of the cryoprobe reached −35 °C and the radius of the frozen region was 2 mm. To evaluate the temperature distribution, a numerical simulation was conducted. The temperature distribution in the frozen region and the heat transfer coefficient was discussed.

Sign in / Sign up

Export Citation Format

Share Document