download pdf - Institut für Umweltphysik - Ruprecht-Karls-Universität ...

More documents

Recommendations

Info

128 CHAPTER 3. TERRESTRIAL SYSTEMS 3.1.7 Modelling water flow and solute transport in heterogeneous soil Participating scientist Hans-Jörg Vogel, Isabelle Cousin, Olaf Ippisch Abstract Flow and transport in soil is governed by the heterogeneous structure of the material. In this project we consider the structure using different concepts: direct measurement, statistical description and modelling structure formation. Based on this rough representation we estimate water flow and solute transport. This is possible because the processes are dissipative. A B C Figure 3.7: Soil profile with three horizons (A, B, C) and the distribution of a dye tracer (left), modelled structural components: correlated random fields and earthworm burrows (middle), and predicted tracer distribution (right). Background The quantitative understanding of flow and transport in soil is hampered by the heterogeneous structure of the material which cannot be represented by a meaningful average value. This is typically true at any spatial scale. To predict the movement of chemicals between the soil surface and groundwater this structure has to be represented adequately. Funding Deutscher Akademische Auslandsdienst (DAAD, PROCOPE project). Methods and results In this project we used a dye tracer in a field experiment on arable soil to visualize the tracer distribution after a cumulative infiltration of 50 mm of water. To model this experiment, the structure of the soil was represented using three different approaches: i) direct measurement of the soil horizons in the field (A,B,and C in the figure) and the measurement of the related hydraulic properties in lab experiments; ii) description of the mesoscopic heterogeneity inside the horizons by an estimated covariance function in the A and C horizon; iii) modelling earthworm burrows in the middle, compacted horizon (B) by a model which mimics the formation of these macropores. As a result we obtain the continuous parameter field (hydraulic properties) of the entire experimental domain. Hence, the 3D velocity field of water could be calculated by solving Richards’ Equation numerically. Subsequently, solute transport was simulated assuming a convection-dispersion type of transport locally. Our model predicted the main characteristics of the experiment. It demonstrates that a rough description of the structure together with a rough measurement/estimation of the related material properties can be sufficient to come up with reliable predictions. Outlook/Future work The further development of non-invasive techniques to measure the heterogeneous structure of the subsurface, together with an better understanding of structure forming processes will improve our ability to quantitatively understand water flow and solute transport in soil. Main publication Vogel et al. [2005b]
3.1. SOIL PHYSICS 129 3.1.8 Unsaturated Flow in Strongly Heterogeneous Porous Media Participating scientist Olaf Ippisch, Interdisciplinary Center for Scientific Computing Abstract Numerical models for the simulation of flow and transport in strongly heterogeneous porous media have been developed and optimized for speed, robustness and usability. The models were used to simulate laboratory and field experiments and were used for parameter estimation from multi-step outflow experiments. Figure 3.8: Simulation of water infiltration in a macroporous soil Background Natural porous media are often strongly heterogeneous. This can influence the flow patterns considerably, resulting in preferential flow or macropore flow which have to be taken into account to get reliable predictions of solute transport. One way to handle this problem is the use of homogenization approaches to get a set of effective parameters for the porous medium as a whole. However, if the heterogeneous structures are large in comparison to the scale of interest this is no longer possible. An alternative strategy is the determination of the soil structure (e.g. with x-ray tomography, geoelectrics, georadar) and the direct simulation of the flow field. Special numerical problems arise for parameter fields changing on a very small scale with sometimes highly nonlinear parameter functions resulting in poor convergence of the linear and nonlinear solvers. Funding <strong>Institut</strong>e for Informatics, University of Heidelberg Methods and results The developed model µϕ uses the Levenberg-Marquardt-Algorithm for parameter estimation with sensitivities derived by external numerical differentiation. The forward model solves Richards’ equation or twophaseflow equations using a cell-centered finite-volume scheme with full-upwinding in space and an implicit Euler scheme in time. Linearization of the nonlinear equations is done by an inexact Newton- Method with line search. The linear equations are solved with an algebraic multigrid solver. For the time solver the time step is adopted automatically. Brooks-Corey and van Genuchten parametrizations as well as cubic splines can be used for the hydraulic functions. Solute transport was discretized using a higher-order Godonov method with a minmod slope limiter for the convective part and a finite-volume scheme for the diffusive term. It is currently limited to steady-state flow conditions. Outlook/Future work The model will be ported to the new base library Dune which facilitates the parallelization and the use of different grid types. Parameter estimation is currently expanded to evaporation experiments. The stability and usability of the twophase will be improved and the solute transport model expanded to nonsteady-state flow conditions. Main publications Vogel et al. [2005b]
Page 1:
Institut für Umweltphysik und Arbe
Page 5 and 6:
Contents 1 Introduction/Overview of
Page 7 and 8:
CONTENTS 7 3.2.1 Glaciological pilo
Page 9:
Introduction In Heidelberg, environ
Page 13 and 14:
Overview Summary Atmospheric resear
Page 15 and 16:
2.1. TROPOSPHERIC RESEARCH GROUP 15
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33:
Page 36 and 37:
36 CHAPTER 2. ATMOSPHERE AND REMOTE
Page 38 and 39:
Page 40 and 41:
Page 42 and 43:
Page 45 and 46:
2.3. RADIATIVE TRANSFER 45 2.3 Radi
Page 47 and 48:
2.3. RADIATIVE TRANSFER 47 Funding
Page 49 and 50:
2.3. RADIATIVE TRANSFER 49 2.3.2 Ox
Page 51 and 52:
2.3. RADIATIVE TRANSFER 51 2.3.4 At
Page 53:
2.3. RADIATIVE TRANSFER 53 Rothman,
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79: 78 CHAPTER 2. ATMOSPHERE AND REMOTE
Page 95 and 96: 2.6. MARHAL - MODELING OF MARINE AN
Page 105 and 106: 2.7. CARBON CYCLE GROUP 105 2.7 Car
Page 107 and 108: 2.7. CARBON CYCLE GROUP 107 Diploma
Page 109 and 110: 2.7. CARBON CYCLE GROUP 109 2.7.2 S
Page 111 and 112: 2.7. CARBON CYCLE GROUP 111 2.7.4 I
Page 113: 2.7. CARBON CYCLE GROUP 113 Schell,
Page 117 and 118: 3.1. SOIL PHYSICS 117 Overview We s
Page 119 and 120: 3.1. SOIL PHYSICS 119 In November 2
Page 121 and 122: 3.1. SOIL PHYSICS 121 Major Achieve
Page 123 and 124: 3.1. SOIL PHYSICS 123 3.1.2 X-ray a
Page 125 and 126: 3.1. SOIL PHYSICS 125 3.1.4 Near In
Page 127: 3.1. SOIL PHYSICS 127 3.1.6 Free Pa
Page 131 and 132: 3.1. SOIL PHYSICS 131 3.1.10 Monito
Page 133 and 134: 3.1. SOIL PHYSICS 133 3.1.12 3D Ful
Page 135 and 136: 3.1. SOIL PHYSICS 135 References Ba
Page 137 and 138: 3.2. ICE AND CLIMATE 137 3.2 Ice an
Page 139 and 140: 3.2. ICE AND CLIMATE 139 regions) a
Page 141 and 142: 3.2. ICE AND CLIMATE 141 3.2.2 Cons
Page 143 and 144: 3.2. ICE AND CLIMATE 143 3.2.4 Clim
Page 145 and 146: 3.2. ICE AND CLIMATE 145 3.2.6 Nove
Page 147: 3.2. ICE AND CLIMATE 147 Preunkert,
Page 151 and 152: 4.1. GROUNDWATER AND PALEOCLIMATE 1
Page 161 and 162: 4.2. LAKE RESEARCH (LIMNOPHYSICS) 1
Page 167: Small-Scale Air-Sea Interaction 5.1
Page 170 and 171: 170 CHAPTER 5. SMALL-SCALE AIR-SEA
Page 178 and 179:
178 CHAPTER 5. SMALL-SCALE AIR-SEA
Page 180 and 181:
Page 182 and 183:
Page 185:
Forschungsstelle “Radiometrie”
Page 188 and 189:
188 CHAPTER 6. FORSCHUNGSSTELLE “
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Page 204 and 205:
Page 206 and 207:
Page 209 and 210:
7.1. PEER REVIEWED PUBLICATIONS 209
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
7.2. GREY PUBLICATIONS 215 Grey Pub
Page 217 and 218:
7.3. PHD THESES 217 PhD Theses Baye
Page 219 and 220:
7.4. DIPLOMA THESES 219 Diploma The
Page 221 and 222:
7.5. INVITED TALKS 221 Invited Talk
Page 223 and 224:
7.5. INVITED TALKS 223 Pundt, I. 20
Page 225:
Institut für Umweltphysik Im Neuen
show all

download pdf - Institut für Umweltphysik - Ruprecht-Karls-Universität ...

Create successful ePaper yourself

Delete template?

Save as template?