Spatially Non-Uniform Time-Step Adaptation for Functional Outputs in Unsteady Flow Problems

2010 ◽  
Author(s):  
Karthik Mani ◽  
Dimitri Mavriplis
Keyword(s):  
Unsteady Flow ◽  
Time Step ◽  
Flow Problems

Is Hydraulics Over-Used or Under-Used in Storm Drainage?

1994 ◽  
Vol 29 (1-2) ◽  
pp. 53-61
Author(s):  
Ben Chie Yen
Keyword(s):  
Unsteady Flow ◽  
Computational Time ◽  
Time Step ◽  
Flow Routing ◽  
Kinematic Wave Equation ◽  
Storm Drainage ◽  
Saint Venant Equations ◽  
Unsteady Flow Routing ◽  
Selection Of

Urban drainage models utilize hydraulics of different levels. Developing or selecting a model appropriate to a particular project is not an easy task. Not knowing the hydraulic principles and numerical techniques used in an existing model, users often misuse and abuse the model. Hydraulically, the use of the Saint-Venant equations is not always necessary. In many cases the kinematic wave equation is inadequate because of the backwater effect, whereas in designing sewers, often Manning's formula is adequate. The flow travel time provides a guide in selecting the computational time step At, which in turn, together with flow unsteadiness, helps in the selection of steady or unsteady flow routing. Often the noninertia model is the appropriate model for unsteady flow routing, whereas delivery curves are very useful for stepwise steady nonuniform flow routing and for determination of channel capacity.

scholarly journals Marker Re-Distancing (MRD) Algorithm for High-Fidelity Interface Tracking on Arbitrary Meshes

2017 ◽  
Author(s):  
Patrick T. Greene ◽  
Robert Nourgaliev ◽  
Samuel P. Schofield
Keyword(s):  
Material Flow ◽  
High Order ◽  
Interface Tracking ◽  
High Fidelity ◽  
Time Step ◽  
Tracking Method ◽  
Flow Problems ◽  
Constrained Minimization Problem ◽  
Irregular Meshes ◽  
Stability Time

A new sharp high-order interface tracking method for multi-material flow problems on unstructured meshes is presented. This marker re-distancing (MRD) method is designed to work accurately and robustly on unstructured, generally highly distorted meshes, necessitated by applications within ALE-based hydrocodes. The method is a hybrid of a Lagrangian marker tracking method and a novel discontinuous Galerkin (DG) projection based level set re-distancing algorithm. The re-distancing method is formulated as a constrained minimization problem and is shown to obtain arbitrary orders of convergence for smooth interfaces. High-order (>2nd) re-distancing on irregular meshes is a must for applications were the interfacial curvature is important for the underlying physics, such as surface tension, wetting, and detonation shock dynamics. Since no PDE is solved for re-distancing, the method does not have a stability time step restriction, which is particularly useful in combination with AMR, used here to efficiently resolve fine interface features. In addition, the method can robustly handle discontinuities in the distance function without explicit utilization of solution limiters. Results will be shown for a number of different interface geometries, which will demonstrate the method’s capability of obtaining high-fidelity results on arbitrary meshes.

Unsteady Flow Calculations by Numerical Methods

1972 ◽  
Vol 94 (2) ◽  
pp. 457-465 ◽  
Author(s):  
V. L. Streeter
Keyword(s):  
Numerical Methods ◽  
Boundary Conditions ◽  
Unsteady Flow ◽  
Various Boundary Conditions ◽  
Flow Problems ◽  
Velocity Flow ◽  
Compressed Gas ◽  
Order Of Magnitude ◽  
Metal Pipes ◽  
Complex Boundary

A review of methods of handling unsteady flow problems in metal pipes by numerical methods is undertaken. The characteristic method, typifying explicit methods, and the centered implicit method are developed, including the manner various boundary conditions are introduced into the solutions. High velocity flow is briefly reviewed, i.e., flow cases with the velocity of flow of the same order of magnitude as the pulse wave speed. Three complex boundary conditions are examined: turbomachinery, column separation, and the compressed gas accumulator.

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