Impact of Time Step Size on Different Cumulus Parameterization Schemes in the Numerical Simulation of a Heavy Rainfall Event Over Tamil Nadu, India

2021 ◽  
Author(s):  
Kuvar Satya Singh ◽  
Subbareddy Bonthu ◽  
Prasad K. Bhaskaran ◽  
R. Purvaja ◽  
R. Ramesh
Keyword(s):  
Numerical Simulation ◽  
Tamil Nadu ◽  
Heavy Rainfall ◽  
Rainfall Event ◽  
Cumulus Parameterization ◽  
Heavy Rainfall Event ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Cumulus Parameterization Schemes

scholarly journals Maintenance condition of back-building squall-line in a numerical simulation of a heavy rainfall event in July 2010 in Western Japan

2018 ◽  
Vol 20 (1) ◽  
pp. e880 ◽  
Author(s):  
Ryuji Yoshida ◽  
Seiya Nishizawa ◽  
Hisashi Yashiro ◽  
Sachiho A. Adachi ◽  
Tsuyoshi Yamaura ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Heavy Rainfall ◽  
Rainfall Event ◽  
Squall Line ◽  
Heavy Rainfall Event ◽  
Western Japan

A Numerical Coning Model

1970 ◽  
Vol 10 (04) ◽  
pp. 418-424 ◽  
Author(s):  
J.P. Letkeman ◽  
R.L. Ridings
Keyword(s):  
Numerical Simulation ◽  
Finite Difference ◽  
Two Dimensions ◽  
Solution Technique ◽  
Production Rates ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Size Limitation ◽  
Single Well

Abstract The numerical simulation of coning behavior bas been one of the most difficult applications of numerical analysis techniques. Coning simulations have generally exhibited severe saturation instabilities in the vicinity of the well unless time-step sizes were severely restricted. The instabilities were a result of using mobilities based on saturations existing at the beginning of the time step. The time-step size limitation, usually the order of a few minutes, resulted in an excessive amount of computer time required to simulate coning behavior. This paper presents a numerical coning model that exhibits stable saturation and production behavior during cone formation and after breakthrough. Time-step sizes a factor of 100 to 1,000 times as large as those previously possible may be used in the simulation. To ensure stability, both production rates and mobilities are extrapolated production rates and mobilities are extrapolated implicitly to the new time level. The finite-difference equations used in the model are presented together with the technique for incorporating the updated mobilities and rates. Example calculations which indicate the magnitude of the time-truncation errors are included. Various factors which affect coning behavior are discussed. Introduction The usual formulation of numerical simulation models for multiphase flow involves the evaluation of flow coefficient terms at the beginning of a time step and assumes that these terms do not change over the time step. These assumptions are valid only if the values of pressure and saturation in the system do not change significantly over the time step. The design of a finite-difference model to evaluate coning behavior of gas or water in a single well usually results in a model which uses radial coordinates. A two-dimensional single-well model is illustrated in Fig. 1. This type of model will often produce finite-difference blocks with pore volumes less than 1 bbl near the wellbore while producing large blocks with pore volumes greater producing large blocks with pore volumes greater than 1 million bbl near the external radius. If one chooses to use a reasonable time-step size of, say, 1 to 10 days, then normal well rates would result in a flow of several hundred pore volumes per time step through blocks near the wellbore. Therefore the assumption that saturations remain constant, for the purpose of coefficient evaluation, is not valid. Welge and Weber presented a paper on water coning which recognized the limitation of using explicit coefficients and applied an arbitrary limitation on the maximum saturation change over a time step. While this method is workable for a certain class of problems, it is not rigorous and is not generally applicable. In 1968, Coats proposed a method to solve the gas percolation problem which is similar in that it also results from explicit mobilities. This proposal involved adjusting the relative permeability to gas at the beginning of the time step so that an individual block would not be over-depleted of gas during a time step. This method is not conveniently extended to two dimensions nor to coning problems where a block is voided many times during a time step. Blair and Weinaug explored the problems resulting from explicitly determined coefficients and formulated a coning model with implicit mobilities and a solution technique utilizing Newtonian iteration. While this method is rigorous, achieving convergence on certain problems is difficult and, in many cases, time-step size is still severely restricted. In addition to the problems resulting from explicit flow-equation coefficients in coning models, the specification of rates requires attention to ensure that the saturations remain stable in the vicinity of the producing block. SPEJ P. 418

scholarly journals Numerical Simulations and Analysis of June 16, 2010 Heavy Rainfall Event over Singapore Using the WRFV3 Model

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
B. H. Vaid
Keyword(s):  
Numerical Simulations ◽  
Heavy Rainfall ◽  
Global Analysis ◽  
Heavy Rain ◽  
Rainfall Event ◽  
Cumulus Parameterization ◽  
Heavy Rainfall Event ◽  
Convective System ◽  
Rain Event ◽  
Simulated Precipitation

The Numerical Simulations of the June 16, 2010, Heavy Rainfall Event over Singapore are highlighted by an unprecedented precipitation which produced widespread, massive flooding in and around Singapore. The objective of this study is to check the ability of Weather Research Forecasting version 3 (WRFV3) model to predict the heavy rain event over Singapore. Results suggest that simulated precipitation amounts are sensitive to the choice of cumulus parameterization. Various model configurations with initial and boundary conditions from the NCEP Final Global Analysis (FNL), convective and microphysical process parameterizations, and nested-grid interactions have been tested with 48-hour (June 15–17, 2010) integrations of the WRFV3. The spatial distributions of large-scale circulation and dynamical and thermodynamical fields have been simulated reasonably well in the model. The model produced maximum precipitation of ~5 cm over Changi airport which is very near to observation (6.4 cm recorded at Changi airport). The model simulated dynamic and thermodynamic features at 00UTC of June 16, 2010, lead to understand the structure of the mesoscale convective system (MCS) that caused the extreme precipitation over Singapore. It is observed that Singapore heavy rain was the result of an interaction of synoptic-scale weather systems with the mesoscale features.

Research on the Uncertainty Analysis in CFD Simulation of the Dredging Dustpan

2016 ◽  
Author(s):  
Yu Lu ◽  
Ankang Hu ◽  
Xin Chang
Keyword(s):  
Numerical Simulation ◽  
Unsteady Flow ◽  
Uncertainty Analysis ◽  
Velocity Ratio ◽  
Step Size ◽  
Time Step ◽  
Outlet Cross Section ◽  
Time Step Size ◽  
Grid Convergence ◽  
Benchmark Database

The main focus of this paper is on the uncertainty analysis methodology and procedure in CFD recommended by 22nd ITTC and the benchmark database for the verification and validation of the results of dredging dustpan’s inlet and outlet cross-section velocity ratio coefficient viur. Compared with the previous uncertainty analysis of CFD focused on the fluid grid-convergence in the steady flow, which is less to consider other factors that may affect the accuracy of the results of numerical simulation, this study compensates for this deficiency and implements the grid-convergence and time-step-size-convergence studies respectively by using three types of grids and time step sizes with refinement ratio under the condition of unsteady flow. Through confirming the validity of CFD uncertainty analysis, the agreement between the numerical simulation correction values from the grid-convergence and time-step-size-convergence and the benchmark test data is found to be quite satisfactory. The results obtained in this study have shown that it is indispensable to carry out the time-step-size-convergence studies for CFD uncertainty analysis during the unsteady flow calculation because the numerical simulation errors respectively caused by the grid and time-step-size in the convergence study have the same order of magnitude. In further the present study of simultaneously conducting both grid-convergence and time-step-size-convergence is demonstrated efficient and effective in the CFD uncertainty analysis.

scholarly journals Numerical simulation of a heavy rainfall event during the PRE-STORM Experiment

1997 ◽  
Vol 33 (4) ◽  
pp. 783-799 ◽  
Author(s):  
Wenjie Zhao ◽  
James A. Smith ◽  
A. Allen Bradley
Keyword(s):  
Numerical Simulation ◽  
Heavy Rainfall ◽  
Rainfall Event ◽  
Heavy Rainfall Event
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