scholarly journals Variable Saturation Infiltration Model for Highly Vegetated Regions

2016 ◽  
Author(s):  
James Polsinelli ◽  
M. Levent Kavvas
Keyword(s):  
Water Content ◽  
Pore Space ◽  
Soil Column ◽  
Richards Equation ◽  
Universal Method ◽  
Infiltration Capacity ◽  
Rectangular Profile ◽  
Numerical Effort ◽  
Non Linear ◽  
Non Linear System

Abstract. Observations have been made in studies that in watersheds with moist soils and lush vegetation, water does not pond on the soil surface, even during significant rainfall events. In these cases, all the water infiltrates into the soil. Furthermore, the water content in the pore space is below saturation. The tools for modeling such situations are limited. A universal method for estimating groundwater in the unsaturated zone is the Richards' equation, a non linear system of 1D or 3D equations based on physical flow principles. While effective, the difficulties in solving Richards' equation can pose a significant problem in a complex system, which may require extensive amounts of calibration and numerical effort in procuring a solution. A second method is based on the idea of approximating the movement of moisture through the soil as a rectangular profile, e.g. assuming that the water moves through a soil column like a piston. Rectangular profile methods have been developed in the past for cases in which ponding occurs at the surface, and the water content inside the column is at saturation. More general rectangular profile methods allow the water in the column to move at sub-saturation. Both of these existing methods involve solving a non linear algebraic equation for the hydrologic system, involving constant flux at the boundary, due to a wetting event such as rainfall. The method proposed in this article may be used for situations in which the soil does not become saturated, and the soil and rainfall properties, specifically the rates of hydraulic conductance and rate of rainfall respectively, are allowed to vary in space or time. The method proposed is based on a simple principle in infiltration hydrology, that the rate at which water will infiltrate through the soil equilibrates with the rate of rainfall, when the rate of rainfall is smaller than the infiltration capacity of the soil. In application, this method does not require the solution of a non linear algebraic (or differential) system of equations, thus affording modelers computational economy. Furthermore, this new method can be made to interact with the saturated profile methods in the event that the rainfall overwhelms the ability of soil to absorb moisture. If this happens, a portion of the field will come to saturation while other parts will be below saturation. The sub-saturation models can be made to interact with the redistribution and evapotranspiration processes by providing the initial and boundary condition for those events.

LysimeterGEO for modelling soil-vegetation-atmosphere 1D system in the Critical Zone

2021 ◽  
Author(s):  
Concetta D'Amato ◽  
Niccolò Tubini ◽  
Riccardo Rigon
Keyword(s):  
Water Stress ◽  
Soil Column ◽  
Critical Zone ◽  
Stress Factor ◽  
Richards Equation ◽  
Travel Times ◽  
One Dimensional ◽  
Solute Fluxes ◽  
The One ◽  
Non Linear System

<p>Measuring and modelling of water and solute fluxes in the Critical Zone across soil-vegetation-atmosphere system is nowadays a very important challenge because of the complexity of both soil and plants. Considering the one-dimensional problem, we implement a virtual lysimeter model, LysimeterGEO, in which we coupled infiltration and evapotranspiration by using stress factor (Jarvis, 1976; Ball et al., 1987), with which we can compute effective evapotranspiration and remove it from Richards’ equation balance (Casulli and Zanolli, 2010).</p><p>As regards the IT implementation, LysimeterGEO is a system of components built upon the Object Modelling System v3 (OMS3). The infiltration component of the virtual lysimeter is WHETGEO 1D - Water, Heat and Transport in GEOframe (Tubini N. 2021), which solves the mass and energy balance for the one-dimensional case. The mass balance is represented by the Richards equation and the non-linear system is solved using the nested Newton algorithm (Casulli and Zanolli, 2010). Evapotranspiration flows are instead estimated using the GEOframe-Prospero model (Bottazzi M. 2020) which estimates the effective transpiration through the equilibrium temperature of the canopy as a function of the stomatal conductance. Finally, the transpiration is calculated starting from the method of Schymanski and Or (2017) and modified by including the dependence on the transpiring surface, the model of conductance of the stomata, as well as the conservation of mass. In LysimeterGEO the interaction between infiltration and evapotranspiration is made possible by BrokerGEO component (D’Amato C. 2021), which computes the water stress factor for vegetation by using Jarvis or Ball-Berry model. BrokerGEO computes the water stress factor considering the water content information by WHETGEO in each control volumes of the soil column discretization. Moreover, it computes a representative water stress factor for the whole column of soil for the evapotranspiration component. Finally, the density root distribution is considered to remove water into the soil used for evapotranspiration flows.</p><p>The modelling of water and solute fluxes across soil-vegetation-atmosphere is made possible by implementation of travel times of waters within vegetation, the growing of the roots and in general the growing of the plants. The idea of a joint infiltration-evapotranspiration model allows us to investigate also problems related to radical growth and the different effect of roots on vegetation. Furthermore, the implementation of travel times on a vegetation scale allows a careful analysis of the behaviour of the same as the soil moisture conditions vary.</p>

scholarly journals A Modified Green-Ampt Model and Parameter Determination for Water Infiltration in Fine-textured Soil with Coarse Interlayer

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 787
Author(s):  
Shuai Chen ◽  
Xiaomin Mao ◽  
Chunying Wang
Keyword(s):  
Water Content ◽  
Soil Column ◽  
Soil Layer ◽  
Water Infiltration ◽  
Richards Equation ◽  
Parameter Determination ◽  
Wetting Front ◽  
Soil Matrix ◽  
Simulation Results ◽  
Two Parameters

A modified Green-Ampt model was developed to simulate water infiltration in fine-textured soil with a coarse interlayer. Because under such a soil structure, the two soils may not be fully saturated during infiltration, the model introduced two parameters—that is, the saturation coefficients a and b, to reflect the incomplete saturation condition and their influence on infiltration processes. In order to analyze the variation pattern of the two parameters in the above proposed model, scenarios were set for soil column infiltration in fine-textured soil with a coarse interlayer under different buried depths. A Richards equation-based model (RE-Model) was built for simulating the above scenarios and to obtain the evolution of soil water content along the soil profiles. Simulation results show that the infiltration rate decreased to a constant value when the wetting front crossed the upper interface between the fine and coarse soil layer. The soil matrix suction (ψ2) at the upper interface remained unchanged after the wetting front advanced into the coarse layer, and the steady value of ψ2 showed a linear relationship with the buried depth of the coarse layer. Based on the simulation results of the RE-Model, a method was proposed to determine the saturation coefficients related to the relative hydraulic conductivity and water content at ψ2 in the modified Green-Ampt model. Then, the modified model was tested under various infiltration conditions with different soil layered structures, and the results showed good agreement with the experimental data.

A novel LSSVM-L Hammerstein model structure for system identification and nonlinear model predictive control of CSTR servo and regulatory control

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Akshaykumar Naregalkar ◽  
Subbulekshmi Durairaj
Keyword(s):  
Linear System ◽  
Regulatory Control ◽  
Hammerstein Model ◽  
Support Vector ◽  
Model Structure ◽  
Linear Dynamics ◽  
Vector Machines ◽  
Non Linear ◽  
Laguerre Filters ◽  
Non Linear System

Abstract A continuous stirred tank reactor (CSTR) servo and the regulatory control problem are challenging because of their highly non-linear nature, frequent changes in operating points, and frequent disturbances. System identification is one of the important steps in the CSTR model-based control design. In earlier work, a non-linear system model comprises a linear subsystem followed by static nonlinearities and represented with Laguerre filters followed by the LSSVM (least squares support vector machines). This model structure solves linear dynamics first and then associated nonlinearities. Unlike earlier works, the proposed LSSVM-L (least squares support vector machines and Laguerre filters) Hammerstein model structure solves the nonlinearities associated with the non-linear system first and then linear dynamics. Thus, the proposed Hammerstein’s model structure deals with the nonlinearities before affecting the entire system, decreasing the model complexity and providing a simple model structure. This new Hammerstein model is stable, precise, and simple to implement and provides the CSTR model with a good model fit%. Simulation studies illustrate the benefit and effectiveness of the proposed LSSVM-L Hammerstein model and its efficacy as a non-linear model predictive controller for the servo and regulatory control problem.

scholarly journals Local radon flux maxima in the quaternary sediments of Schleswig–Holstein (Germany)

2021 ◽  
Author(s):  
Johannes Albert ◽  
Maximilian Schärf ◽  
Frieder Enzmann ◽  
Martin Waltl ◽  
Frank Sirocko
Keyword(s):  
Water Content ◽  
Pore Space ◽  
Mineralogical Composition ◽  
Fault System ◽  
Near Surface ◽  
Salt Diapirism ◽  
The North ◽  
Radon Flux ◽  
Published Evidence ◽  
Tectonically Active

AbstractThis paper presents radon flux profiles from four regions in Schleswig–Holstein (Northern Germany). Three of these regions are located over deep-rooted tectonic faults or salt diapirs and one is in an area without any tectonic or halokinetic activity, but with steep topography. Contrary to recently published studies on spatial patterns of soil radon gas concentration we measured flux of radon from soil into the atmosphere. All radon devices of each profile were deployed simultaneously to avoid inconsistencies due to strong diurnal variations of radon exhalation. To compare data from different seasons, values had to be normalized. Observed radon flux patterns are apparently related to the mineralogical composition of the Quaternary strata (particularly to the abundance of reddish granite and porphyry), and its grain size (with a flux maximum in well-sorted sand/silt). Minimum radon flux occurs above non-permeable, clay-rich soil layers. Small amounts of water content in the pore space increase radon flux, whereas excessive water content lessens it. Peak flux values, however, are observed over a deep-rooted fault system on the eastern side of Lake Plön, i.e., at the boundary of the Eastholstein Platform and the Eastholstein Trough. Furthermore, high radon flux values are observed in two regions associated with salt diapirism and near-surface halokinetic faults. These regions show frequent local radon flux maxima, which indicate that the uppermost strata above salt diapirs are very inhomogeneous. Deep-rooted increased permeability (effective radon flux depth) or just the boundaries between permeable and impermeable strata appear to concentrate radon flux. In summary, our radon flux profiles are in accordance with the published evidence of low radon concentrations in the “normal” soils of Schleswig–Holstein. However, very high values of radon flux are likely to occur at distinct locations near salt diapirism at depth, boundaries between permeable and impermeable strata, and finally at the tectonically active flanks of the North German Basin.

On a non-linear system for shape memory alloys

1990 ◽  
Vol 2 (1) ◽  
pp. 65-76 ◽  
Author(s):  
Ph. B�nilan ◽  
D. Blanchard ◽  
H. Ghidouche
Keyword(s):  
Linear System ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Non Linear ◽  
Non Linear System

Position Control of Hydraulic Actuators Using Fuzzy Pulse Width Modulation (PWM)

2015 ◽  
Vol 735 ◽  
pp. 294-298 ◽  
Author(s):  
Wei Ying Lai ◽  
Nurfarahin Onn ◽  
Collin Howe Hing Tang ◽  
Mohamed Hussein
Keyword(s):  
Fuzzy Logic ◽  
Pulse Width ◽  
Pulse Width Modulation ◽  
Solenoid Valve ◽  
Operating Conditions ◽  
Hydraulic Actuators ◽  
Non Linear ◽  
Fuzzy Logic Approach ◽  
Logic Approach ◽  
Non Linear System

Hydraulic actuators are widely employed for industrial automation for its high power over weight ratio, functionality in tough operating conditions and low cost. However, the dynamics of hydraulic systems are non-linear and the system subjected to non-smooth and discontinuous non-linearities due to directional change of valve opening, friction, valve overlap and changes of hydraulic pressure acted on valve spool. Taking into account the effect of nonlinear parameter variations such as bulk modulus, compressibility of oil or viscosity of oil, fuzzy logic approach is chosen. Fuzzy control can adapt the inconstant working condition and non-linear system alongside of its robustness. For PWM controlled hydraulic component such as solenoid valve, effective approximation of the flow properties in a solenoid valve is essential. In this paper, the effect of fuzzy logic approach incorporated on pulse width modulation (PWM) controlled hydraulic system is to be investigated and experimentally verified.

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