George W. Cole

A Simulation Model of Daily Wind Erosion Soil Loss

ABSTRACT EPICs (Erosion Productivity Impact Calculator) wind erosion submodel is described in terms of the equations and concepts needed for interfacing the wind erosion equation with EPIC. The required equations are presented following an analysis of the wind erosion equation literature which shows how the wind erosion equation was developed from short-term data. This analysis is based on viewing the soil loss as a time and space integration of a surface soil flux. The wind erosion equation is then partitioned into those parts that represent the short-term effects and the integration process. From this it is seen how one might ideally modify the wind erosion equation. The analyses point the way for future improvements in soil loss prediction equations. The results of the five 50-yr simulations are also presented.

The Application of Control Systems Theory to the Analysis of Ventilated Animal Housing Environments

ABSTRACT CONTROL theory terminology and block diagram-ming techniques are applied to the analysis of animal environment control systems for the purpose of unifying the apparently diverse terminology and clarifying the concepts of environmental control. The importance of the control strategy is stressed for comprehension of pre-sent designs and the enhancement of the more com-prehensive control functions of the future which will in-volve digital controllers. Two examples of animal en-vironmental control systems are analyzed using the con-trol system concepts presented.

A Probability Criterion for Acceptable Soil Erosion

ABSTRACT THE soil erosion process is presently considered acceptable whenever the predicted mean of the soil erosion distribution is equal to or less than the soil loss tolerance. Another criterion is proposed, which limits the soil erosion to a specified range with an acceptable degree of risk. The rationale, required assumptions, and methods are discussed for determining this criterion, which is a function only of soil productivity. Because of this difficulty in simulation soil erosion, for the time implied by this criterion, a method is suggested for determining a short term erosion criteria

A Method for Determining Field Wind Erosion Rates from Wind-Tunnel-Derived Functions

ABSTRACT THE mass flow rate equation for a convex-shaped field surface subjected to wind erosion is derived by the application of the steady state continuity equation. It is assumed and justified that the soil flow can be idealized as a flux. The resultant equation, predicted on the availability of line-intensity functions (q) developed from wind tunnel studies, is the line integral of the qs around the perimeter of the field at the saltation height. The shape of the field is limited at present to only convex shapes. Fortunately, a typical agricultural field is rectangular. The assumptions implied by this method are stressed and two examples are presented that deal with nonhomogeneous surfaces and both erodible and nonerodible boundaries.

A Stochastic Formulation of Soil Erosion Caused by Wind

ABSTRACT DEVELOPMENT of a new equation to predict soil erosion requires the integration of the surface soil flux vector across the eroding area and for some interval of time. In this paper we analyze the time integration and show that both an arithmetic and statistical average must be considered for prediction. The arithmetic average, which is called the soil erosion, is shown to be a measure which may or may not be random. When random, its statistical mean is called the average soil erosion. For this average, consideration must be given to two time intervals, a soil loss accounting interval and a periodicity associated with the deterministic independent variables. This latter average is shown to be identical with the present measure of wind erosion when the two time intervals are 1 year. A general equation for the statistical average is developed and its use is illustrated by developing specific equations for two different soil loss accounting intervals.

A Linear Ventilation Rate Temperature Controller for a Confined Animal Housing System

ABSTRACT A linear ventilation flow rate controller has been designed using a microprocessor. This design is reviewed with regard to the hardware, software, and system stability. The advantages of software control and its inherent flexibility are also discussed.

Some Wind Erosion Process Measures

ABSTRACT RELATING the various damaging effects of soil erosion by wind to the appropriate measures of the erosion process are critical for controlling and estimating the probable damage. A method is outlined using the conservation of mass and momentum principles showing how the cause and effect measures can be related. The method is demonstrated by applying it to three possible damaging effects, i.e., crop yield, soil loss from the field, and plant damage by abrasion.

The Derivation and Analysis of The Differential Equations for the Air Temperature of the Confined Animal Housing System

ABSTRACT STARTING with the macroscopic energy and mass balance equations, for three control volumes, (inlets, building, and outlets) equations describing the rate of change of building air temperature and mass flow rates are obtained. Application of the ideal gas equation of state in differential form allows for simplification of the temperature equation. Where possible, all simplifying assumptions are analyzed and justified. All equations, including the standard equation cur-rently in use, are compared numerically indicating a maximum difference of 1.0 °C.

Predicting Building Air Temperature Using the Steady State Energy Equation

ABSTRACT PREDICTION of time varying air temperature in an animal housing building is conventionally ac-complished by utilizing the steady periodic solution to the energy equation. This study presents the rationale and data to support use of the steady state equation. Comparisons between the two methods indicate that a maximum difference of about 10 percent can be ex-pected. The concept of the frequency transfer function is utilized for this comparison and for visualizing the im-portance of the bandwidth and amplitude of the system transfer function and forcing function.

A Method to Predict the Performance of Mechanically Ventilated Systems

ABSTRACT THE concept of the Acceptable Weather Space is in-troduced and used in conjunction with the existing concepts of the Climate Space and Conditioning Line to predict system performance. By graphically portraying these spaces, the designer of a ventilation system can visualize the weather conditions under which his system can be expected to operate correctly. A simple nonlinear controlled fan ventilation system is analyzed using this method. The regions where the system operates both correctly and incorrectly are deter-mined along with the regions of system stability