A 2D Finite Volume Non-hydrostatic Atmospheric Model ...

More documents

Recommendations

Info

$Departments of Mathematics and Physics (D-MATH/D ... - RW/CSE$

6.2 Performance improvementThe main part of increase in performance is due to the change in evaluating the local hydrostatic backgroundstate. Instead of doing the time consuming evaluation every time step we merely do it every 10 thtime step. To illustrate the resulting increase in performance we consider a typical simulation of a linear,non-hydrostatic flow past a small Gaussian hill. The simulation is done using the cut-cell approach. Thecomplete list of used parameters is given in table 6.1. For this simulation the number of calls for theprocedure to calculate the local hydrostatic background state has been reduced from 12501 to 1251calls. This reduces the totally used CPU time from about 6500 seconds to about 3400 seconds which isan increase in performance of more than 90%. However, not calling the procedure every time step doesnot have a noticeable impact on the solution. Figure 6.1 shows the result of a simulation where the localhydrostatic background state is evaluated every time step, figure 6.2 the same for every 10 th time step.time integration schemeatmospheremountain heightmountain half widthmountain typehorizontal domain sizevertical domain sizehorizontal cell sizevertical cell size rangenumber of horizontal grid cellsnumber of vertical grid cellsinitial Brunt-Väisälä frequencybottom potential temperatureinitial vertical velocitytime stepintegration timeparameter value unitx-divergence damping coefficientz-divergence damping coefficientAsselin coefficientRayleigh damping coefficientRayleigh damping layer thicknessx-computational mixing coefficientz-computational mixing coefficientleapfrogstratified11000Gaussian4021400300100700.01288100.450000.050.050.050.0290000.00050.0005Table 6.1: Default parameters used for the simulation of a linear, non-hydrostatic flow past a Gaussian hill.--mm-kmkmmm--1/sKm/sss----m--24
elative horizontal velocity u [m/s]relative vertical velocity w [m/s]1000010000900090008000800070007000height [m]60005000height [m]60005000400040003000300020002000100010000−1 −0.5 0 0.5 1widht [m]x 10 40−1 −0.5 0 0.5 1widht [m]x 10 4Figure 6.1: Horizontal and vertical velocity perturbations of a linear, non-hydrostatic flow. Calculationof background state at every time step. The contour interval is 0.001 m/s. Positive valuesare solid blue and negative values are dash-dotted cyan.relative horizontal velocity u [m/s]relative vertical velocity w [m/s]1000010000900090008000800070007000height [m]60005000height [m]60005000400040003000300020002000100010000−1 −0.5 0 0.5 1widht [m]x 10 40−1 −0.5 0 0.5 1widht [m]x 10 4Figure 6.2: As figure 6.1, but background state is calculated every 10 th time step.25
Page 1: A 2D Finite Volume Non-hydrostatic
Page 5: List of figuresFigure 5.1: Illustra
Page 8 and 9: £¤¢¦§©¡¨¥NomenclatureQDamp
Page 12 and 13: 1.2 MotivationIn [6] Wunderlich imp
Page 15: Cc iR iO'0PPc iPc i/OCc iR ih OO'''
Page 18 and 19: €€€uuG tQ ijt s 0tuww€wwt s
Page 20 and 21: ¼¼µ½¼u¼½u}}}3.5 Reconstructi
Page 22 and 23: ÍãååÌÌ ÍãÍãååçããÍn
Page 24 and 25: ðåùÏÕìãããìëxÏìÞÏãÖ
Page 27 and 28: 6
Page 29 and 30: q ijCRJ Zq i , jP 1 Sq p " RJ""q r
Page 31: 5.3 Terrain-following gridThe terra
Page 36 and 37: 6.3 Linear, non-hydrostatic flowWit
Page 38 and 39: 6.3.2 Impact of the corrected diver
Page 40 and 41: 6.3.4 The effects of computational
Page 42 and 43: elative horizontal velocity u [m/s]
Page 44 and 45: vertical velocity w [m/s]8000700060
Page 46 and 47: Figure 6.11: Simulation of a negati
Page 48 and 49: Figure 6.12: Time evolution of maxi
Page 51: References[1] Klemp, J.B., Skamaroc

A 2D Finite Volume Non-hydrostatic Atmospheric Model ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?