|Title: ||Numerical and experimental modelling of microwave applicators|
|Authors: ||Dibben, David|
|Issue Date: ||24-Oct-1995|
|Abstract: ||This thesis presents a time domain finite element method for the solution of microwave
heating problems. This is the first time that this particular technique has been applied
to microwave heating. It is found that the standard frequency domain finite element
method is unsuitable for analysing multimode applicators containing food-like materials
due to a severe ill-conditioning of the matrix equations. The field distribution in multimode
applicators loaded with low loss materials is found to be very sensitive to small
frequency changes. Several solutions at different frequencies are therefore required to
characterise the behaviour of the loaded applicator. The time domain finite element
method is capable of producing multiple solutions at different frequencies when used
with Gaussian pulse excitation; it is therefore ideally suited to the analysis of multimode
applicators. A brief survey of the methods available for the solution of the linear
equations is provided. The performance of these techniques with both the frequency
domain and time domain finite element methods is then studied.
Single mode applicators are also analysed and it is found that the frequency domain
method is superior in these cases. Comparisons are given between the calculated results
and experimental data for both single mode and multimode systems. The importance
of experimental verification being stressed.
The choice of element type is an important consideration for the finite element
method. Three basic types of element are considered; nodal, Whitney edge elements
and linear edge elements. Comparisons of the errors with these elements show that
Whitney elements produce a consistently lower error when post-processing is used to
smooth the solution.
The coupled thermal-electromagnetic problem is investigated with many difficulties
being identified for the application to multimode cavity problems.|
|Appears in Collections:||Theses - Department of Engineering|
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