広告
4面体1次要素
無次元化した熱収支式は次式となります。
\[
\phi=
\frac{\partial\Theta}{\partial\tau}
+V_x\frac{\partial\Theta}{\partial X}
+V_y\frac{\partial\Theta}{\partial Y}
+V_z\frac{\partial\Theta}{\partial Z}
+\frac{\partial q_x^{*}}{\partial X}
+\frac{\partial q_y^{*}}{\partial Y}
+\frac{\partial q_z^{*}}{\partial Z}
=0
\]
内挿関数Niを重み関数に使用すると離散化式は次式となります。
\[
\int_V
\begin{bmatrix}
N_1\\
N_2\\
N_3\\
N_4
\end{bmatrix}
\phi\,dV
=
\int_V
\begin{bmatrix}
0\\
0\\
0\\
0
\end{bmatrix}
dV
=
\begin{bmatrix}
0\\
0\\
0\\
0
\end{bmatrix}
\]
速度、温度は、内挿関数Niを用いてそれぞれ次式で表されます。
\[
\begin{aligned}
V_x&=N_1V_{x,1}+N_2V_{x,2}+N_3V_{x,3}+N_4V_{x,4}
=\begin{bmatrix}N_1&N_2&N_3&N_4\end{bmatrix}
\begin{Bmatrix}V_{x,1}\\V_{x,2}\\V_{x,3}\\V_{x,4}\end{Bmatrix}
=[N]\{V_x\}=0\\[6pt]
V_y&=N_1V_{y,1}+N_2V_{y,2}+N_3V_{y,3}+N_4V_{y,4}=0\\[6pt]
V_z&=N_1V_{z,1}+N_2V_{z,2}+N_3V_{z,3}+N_4V_{z,4}=0\\[6pt]
\Theta&=N_1\Theta_1+N_2\Theta_2+N_3\Theta_3+N_4\Theta_4
\end{aligned}
\]
従って、離散化式は、次式となります。
\[
\begin{aligned}
&\int_V
\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\left(
\frac{\partial\Theta}{\partial\tau}
+V_x\frac{\partial\Theta}{\partial X}
+V_y\frac{\partial\Theta}{\partial Y}
+V_z\frac{\partial\Theta}{\partial Z}
+\frac{\partial q_x^{*}}{\partial X}
+\frac{\partial q_y^{*}}{\partial Y}
+\frac{\partial q_z^{*}}{\partial Z}
\right)dV\\[6pt]
&=
\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial\Theta}{\partial\tau}dV
+V_x\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial\Theta}{\partial X}dV
+V_y\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial\Theta}{\partial Y}dV\\[6pt]
&\quad
+V_z\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial\Theta}{\partial Z}dV
+\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial q_x^{*}}{\partial X}dV
+\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial q_y^{*}}{\partial Y}dV\\[6pt]
&\quad
+\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial q_z^{*}}{\partial Z}dV
\end{aligned}
\]
展開すると
\[
\begin{aligned}
&\int_V
\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\left(
\frac{\partial\Theta}{\partial\tau}
+V_x\frac{\partial\Theta}{\partial X}
+V_y\frac{\partial\Theta}{\partial Y}
+V_z\frac{\partial\Theta}{\partial Z}
+\frac{\partial q_x^{*}}{\partial X}
+\frac{\partial q_y^{*}}{\partial Y}
+\frac{\partial q_z^{*}}{\partial Z}
\right)dV\\[6pt]
&=
\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial\Theta}{\partial\tau}dV
+V_x\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial\Theta}{\partial X}dV
+V_y\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial\Theta}{\partial Y}dV\\[6pt]
&\quad
+V_z\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial\Theta}{\partial Z}dV
+\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial q_x^{*}}{\partial X}dV
+\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial q_y^{*}}{\partial Y}dV\\[6pt]
&\quad
+\int_V\begin{bmatrix}N_1\\N_2\\N_3\\N_4\end{bmatrix}
\frac{\partial q_z^{*}}{\partial Z}dV
\end{aligned}
\]
\[
\begin{aligned}
&={}
\int_V[N]^T\frac{\partial\Theta}{\partial\tau}dV
+V_x\int_V[N]^T\frac{\partial\Theta}{\partial X}dV
+V_y\int_V[N]^T\frac{\partial\Theta}{\partial Y}dV
+V_z\int_V[N]^T\frac{\partial\Theta}{\partial Z}dV\\[6pt]
&+\int_V[N]^T\frac{\partial q_x^{*}}{\partial X}dV
+\int_V[N]^T\frac{\partial q_y^{*}}{\partial Y}dV
+\int_V[N]^T\frac{\partial q_z^{*}}{\partial Z}dV
\end{aligned}
\]
グリーン・ガウスの定理より
\[
\begin{aligned}
&={}
\int_V[N]^T
\frac{[N]\left(\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}\right)}
{\Delta\tau}dV\\[6pt]
&+V_x\int_V[N]^T\frac{\partial[N]\{\Theta\}}{\partial X}dV
+V_y\int_V[N]^T\frac{\partial[N]\{\Theta\}}{\partial Y}dV
+V_z\int_V[N]^T\frac{\partial[N]\{\Theta\}}{\partial Z}dV\\[6pt]
&+\int_S[N]^Tq_x^{*}n_x\,dS
-\int_V\left[\frac{\partial N}{\partial X}\right]^Tq_x^{*}dV\\[6pt]
&+\int_S[N]^Tq_y^{*}n_y\,dS
-\int_V\left[\frac{\partial N}{\partial Y}\right]^Tq_y^{*}dV\\[6pt]
&+\int_S[N]^Tq_z^{*}n_z\,dS
-\int_V\left[\frac{\partial N}{\partial Z}\right]^Tq_z^{*}dV
\end{aligned}
\]
界面に作用する伝熱の項をまとめると
\[
\begin{aligned}
&={}
\int_V[N]^T[N]dV
\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}
{\Delta\tau}\\[6pt]
&+V_x\int_V[N]^T\left[\frac{\partial N}{\partial X}\right]dV\{\Theta\}
+V_y\int_V[N]^T\left[\frac{\partial N}{\partial Y}\right]dV\{\Theta\}
+V_z\int_V[N]^T\left[\frac{\partial N}{\partial Z}\right]dV\{\Theta\}\\[6pt]
&-\int_V\left[\frac{\partial N}{\partial X}\right]^Tq_x^{*}dV
-\int_V\left[\frac{\partial N}{\partial Y}\right]^Tq_y^{*}dV
-\int_V\left[\frac{\partial N}{\partial Z}\right]^Tq_z^{*}dV\\[6pt]
&+\int_S[N]^T(q_x^{*}n_x+q_y^{*}n_y+q_z^{*}n_z)dS
\end{aligned}
\]
熱流束を展開して
\[
\begin{aligned}
&={}
\int_V[N]^T[N]dV
\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}
{\Delta\tau}\\[6pt]
&+V_x\int_V[N]^T\left[\frac{\partial N}{\partial X}\right]dV\{\Theta\}
+V_y\int_V[N]^T\left[\frac{\partial N}{\partial Y}\right]dV\{\Theta\}
+V_z\int_V[N]^T\left[\frac{\partial N}{\partial Z}\right]dV\{\Theta\}\\[6pt]
&-\int_V\left[\frac{\partial N}{\partial X}\right]^T
\left(-\frac{1}{Pe}\frac{\partial\Theta}{\partial X}\right)dV\\[6pt]
&-\int_V\left[\frac{\partial N}{\partial Y}\right]^T
\left(-\frac{1}{Pe}\frac{\partial\Theta}{\partial Y}\right)dV\\[6pt]
&-\int_V\left[\frac{\partial N}{\partial Z}\right]^T
\left(-\frac{1}{Pe}\frac{\partial\Theta}{\partial Z}\right)dV\\[6pt]
&+Nu(\Theta-\Theta_h)\int_S[N]^T dS
\end{aligned}
\]
項ごとに分解して
\[
\begin{aligned}
&={}
\int_V[N]^T[N]dV
\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}
{\Delta\tau}\\[6pt]
&+V_x\int_V[N]^T\left[\frac{\partial N}{\partial X}\right]dV\{\Theta\}
+V_y\int_V[N]^T\left[\frac{\partial N}{\partial Y}\right]dV\{\Theta\}
+V_z\int_V[N]^T\left[\frac{\partial N}{\partial Z}\right]dV\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial X}\right]^T
\frac{\partial\Theta}{\partial X}dV
+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial Y}\right]^T
\frac{\partial\Theta}{\partial Y}dV
+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial Z}\right]^T
\frac{\partial\Theta}{\partial Z}dV\\[6pt]
&+Nu(\Theta-\Theta_h)\int_S[N]^T dS
\end{aligned}
\]
温度を内挿関数で表示して
\[
\begin{aligned}
&={}
\int_V[N]^T[N]dV
\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}
{\Delta\tau}\\[6pt]
&+V_x\int_V[N]^T\left[\frac{\partial N}{\partial X}\right]dV\{\Theta\}
+V_y\int_V[N]^T\left[\frac{\partial N}{\partial Y}\right]dV\{\Theta\}
+V_z\int_V[N]^T\left[\frac{\partial N}{\partial Z}\right]dV\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial X}\right]^T
\frac{\partial[N]\{\Theta\}}{\partial X}dV
+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial Y}\right]^T
\frac{\partial[N]\{\Theta\}}{\partial Y}dV
+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial Z}\right]^T
\frac{\partial[N]\{\Theta\}}{\partial Z}dV\\[6pt]
&+Nu(\Theta-\Theta_h)\int_S[N]^T dS
\end{aligned}
\]
温度は定数なので積分の外に出す
\[
\begin{aligned}
&={}
\int_V[N]^T[N]dV
\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}
{\Delta\tau}\\[6pt]
&+V_x\int_V[N]^T\left[\frac{\partial N}{\partial X}\right]dV\{\Theta\}
+V_y\int_V[N]^T\left[\frac{\partial N}{\partial Y}\right]dV\{\Theta\}
+V_z\int_V[N]^T\left[\frac{\partial N}{\partial Z}\right]dV\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial X}\right]^T
\left[\frac{\partial N}{\partial X}\right]dV\{\Theta\}
+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial Y}\right]^T
\left[\frac{\partial N}{\partial Y}\right]dV\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\int_V\left[\frac{\partial N}{\partial Z}\right]^T
\left[\frac{\partial N}{\partial Z}\right]dV\{\Theta\}
+Nu(\Theta-\Theta_h)\int_S[N]^T dS
\end{aligned}
\]
行列式で表す
\[
=
\int_V
\begin{bmatrix}
N_1N_1&N_1N_2&N_1N_3&N_1N_4\\
N_2N_1&N_2N_2&N_2N_3&N_2N_4\\
N_3N_1&N_3N_2&N_3N_3&N_3N_4\\
N_4N_1&N_4N_2&N_4N_3&N_4N_4
\end{bmatrix}
dV\,
\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}
{\Delta\tau}
\]
対流項
\[
\begin{aligned}
&+V_x\int_V
\begin{bmatrix}
N_1\frac{\partial N_1}{\partial X}&N_1\frac{\partial N_2}{\partial X}&N_1\frac{\partial N_3}{\partial X}&N_1\frac{\partial N_4}{\partial X}\\
N_2\frac{\partial N_1}{\partial X}&N_2\frac{\partial N_2}{\partial X}&N_2\frac{\partial N_3}{\partial X}&N_2\frac{\partial N_4}{\partial X}\\
N_3\frac{\partial N_1}{\partial X}&N_3\frac{\partial N_2}{\partial X}&N_3\frac{\partial N_3}{\partial X}&N_3\frac{\partial N_4}{\partial X}\\
N_4\frac{\partial N_1}{\partial X}&N_4\frac{\partial N_2}{\partial X}&N_4\frac{\partial N_3}{\partial X}&N_4\frac{\partial N_4}{\partial X}
\end{bmatrix}dV\{\Theta\}\\[6pt]
&+V_y\int_V
\begin{bmatrix}
N_1\frac{\partial N_1}{\partial Y}&N_1\frac{\partial N_2}{\partial Y}&N_1\frac{\partial N_3}{\partial Y}&N_1\frac{\partial N_4}{\partial Y}\\
N_2\frac{\partial N_1}{\partial Y}&N_2\frac{\partial N_2}{\partial Y}&N_2\frac{\partial N_3}{\partial Y}&N_2\frac{\partial N_4}{\partial Y}\\
N_3\frac{\partial N_1}{\partial Y}&N_3\frac{\partial N_2}{\partial Y}&N_3\frac{\partial N_3}{\partial Y}&N_3\frac{\partial N_4}{\partial Y}\\
N_4\frac{\partial N_1}{\partial Y}&N_4\frac{\partial N_2}{\partial Z}&N_4\frac{\partial N_3}{\partial Y}&N_4\frac{\partial N_4}{\partial Y}
\end{bmatrix}dV\{\Theta\}\\[6pt]
&+V_z\int_V
\begin{bmatrix}
N_1\frac{\partial N_1}{\partial Z}&N_1\frac{\partial N_2}{\partial Z}&N_1\frac{\partial N_3}{\partial Z}&N_1\frac{\partial N_4}{\partial Z}\\
N_2\frac{\partial N_1}{\partial Z}&N_2\frac{\partial N_2}{\partial Z}&N_2\frac{\partial N_3}{\partial Z}&N_2\frac{\partial N_4}{\partial Z}\\
N_3\frac{\partial N_1}{\partial Z}&N_3\frac{\partial N_2}{\partial Z}&N_3\frac{\partial N_3}{\partial Z}&N_3\frac{\partial N_4}{\partial Z}\\
N_4\frac{\partial N_1}{\partial Z}&N_4\frac{\partial N_2}{\partial Z}&N_4\frac{\partial N_3}{\partial Z}&N_4\frac{\partial N_4}{\partial Z}
\end{bmatrix}dV\{\Theta\}
\end{aligned}
\]
伝導伝熱の項
\[
\begin{aligned}
&+\frac{1}{Pe}\int_V
\begin{bmatrix}
\frac{\partial N_1}{\partial X}\frac{\partial N_1}{\partial X}&\frac{\partial N_1}{\partial X}\frac{\partial N_2}{\partial X}&\frac{\partial N_1}{\partial X}\frac{\partial N_3}{\partial X}&\frac{\partial N_1}{\partial X}\frac{\partial N_4}{\partial X}\\
\frac{\partial N_2}{\partial X}\frac{\partial N_1}{\partial X}&\frac{\partial N_2}{\partial X}\frac{\partial N_2}{\partial X}&\frac{\partial N_2}{\partial X}\frac{\partial N_3}{\partial X}&\frac{\partial N_2}{\partial X}\frac{\partial N_4}{\partial X}\\
\frac{\partial N_3}{\partial X}\frac{\partial N_1}{\partial X}&\frac{\partial N_3}{\partial X}\frac{\partial N_2}{\partial X}&\frac{\partial N_3}{\partial X}\frac{\partial N_3}{\partial X}&\frac{\partial N_3}{\partial X}\frac{\partial N_4}{\partial X}\\
\frac{\partial N_4}{\partial X}\frac{\partial N_1}{\partial X}&\frac{\partial N_4}{\partial X}\frac{\partial N_2}{\partial X}&\frac{\partial N_4}{\partial X}\frac{\partial N_3}{\partial X}&\frac{\partial N_4}{\partial X}\frac{\partial N_4}{\partial X}
\end{bmatrix}dV\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\int_V
\begin{bmatrix}
\frac{\partial N_1}{\partial Y}\frac{\partial N_1}{\partial Y}&\frac{\partial N_1}{\partial Y}\frac{\partial N_2}{\partial Y}&\frac{\partial N_1}{\partial Y}\frac{\partial N_3}{\partial Y}&\frac{\partial N_1}{\partial Y}\frac{\partial N_4}{\partial Y}\\
\frac{\partial N_2}{\partial Y}\frac{\partial N_1}{\partial Y}&\frac{\partial N_2}{\partial Y}\frac{\partial N_2}{\partial Y}&\frac{\partial N_2}{\partial Y}\frac{\partial N_3}{\partial Y}&\frac{\partial N_2}{\partial Y}\frac{\partial N_4}{\partial Y}\\
\frac{\partial N_3}{\partial Y}\frac{\partial N_1}{\partial Y}&\frac{\partial N_3}{\partial Y}\frac{\partial N_2}{\partial Y}&\frac{\partial N_3}{\partial Y}\frac{\partial N_3}{\partial Y}&\frac{\partial N_3}{\partial Y}\frac{\partial N_4}{\partial Y}\\
\frac{\partial N_4}{\partial Y}\frac{\partial N_1}{\partial Y}&\frac{\partial N_4}{\partial Y}\frac{\partial N_2}{\partial Y}&\frac{\partial N_4}{\partial Y}\frac{\partial N_3}{\partial Y}&\frac{\partial N_4}{\partial Y}\frac{\partial N_4}{\partial Y}
\end{bmatrix}dV\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\int_V
\begin{bmatrix}
\frac{\partial N_1}{\partial Z}\frac{\partial N_1}{\partial Z}&\frac{\partial N_1}{\partial Z}\frac{\partial N_2}{\partial Z}&\frac{\partial N_1}{\partial Z}\frac{\partial N_3}{\partial Z}&\frac{\partial N_1}{\partial Z}\frac{\partial N_4}{\partial Z}\\
\frac{\partial N_2}{\partial Z}\frac{\partial N_1}{\partial Z}&\frac{\partial N_2}{\partial Z}\frac{\partial N_2}{\partial Z}&\frac{\partial N_2}{\partial Z}\frac{\partial N_3}{\partial Z}&\frac{\partial N_2}{\partial Z}\frac{\partial N_4}{\partial Z}\\
\frac{\partial N_3}{\partial Z}\frac{\partial N_1}{\partial Z}&\frac{\partial N_3}{\partial Z}\frac{\partial N_2}{\partial Z}&\frac{\partial N_3}{\partial Z}\frac{\partial N_3}{\partial Z}&\frac{\partial N_3}{\partial Z}\frac{\partial N_4}{\partial Z}\\
\frac{\partial N_4}{\partial Z}\frac{\partial N_1}{\partial Z}&\frac{\partial N_4}{\partial Z}\frac{\partial N_2}{\partial Z}&\frac{\partial N_4}{\partial Z}\frac{\partial N_3}{\partial Z}&\frac{\partial N_4}{\partial Z}\frac{\partial N_4}{\partial Z}
\end{bmatrix}dV\{\Theta\}
\end{aligned}
\]
対流伝熱の項
\[
+Nu(\Theta-\Theta_h)\int_S
\begin{bmatrix}
N_1\\N_2\\N_3
\end{bmatrix}dS
\]
内挿関数を形状関数に直す
\[
=
\int_V
\begin{bmatrix}
L_1L_1&L_1L_2&L_1L_3&L_1L_4\\
L_2L_1&L_2L_2&L_2L_3&L_2L_4\\
L_3L_1&L_3L_2&L_3L_3&L_3L_4\\
L_4L_1&L_4L_2&L_4L_3&L_4L_4
\end{bmatrix}
dV\,
\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}
{\Delta\tau}
\]
対流項
\[
\begin{aligned}
&+V_x\int_V\frac{1}{6V}
\begin{bmatrix}
L_1c_{1x}&L_1c_{2x}&L_1c_{3x}&L_1c_{4x}\\
L_2c_{1x}&L_2c_{2x}&L_2c_{3x}&L_2c_{4x}\\
L_3c_{1x}&L_3c_{2x}&L_3c_{3x}&L_3c_{4x}\\
L_4c_{1x}&L_4c_{2x}&L_4c_{3x}&L_4c_{4x}
\end{bmatrix}dV\{\Theta\}\\[6pt]
&+V_y\int_V\frac{1}{6V}
\begin{bmatrix}
L_1c_{1y}&L_1c_{2y}&L_1c_{3y}&L_1c_{4y}\\
L_2c_{1y}&L_2c_{2y}&L_2c_{3y}&L_2c_{4y}\\
L_3c_{1y}&L_3c_{2y}&L_3c_{3y}&L_3c_{4y}\\
L_4c_{1y}&L_4c_{2y}&L_4c_{3y}&L_4c_{4y}
\end{bmatrix}dV\{\Theta\}\\[6pt]
&+V_z\int_V\frac{1}{6V}
\begin{bmatrix}
L_1c_{1z}&L_1c_{2z}&L_1c_{3z}&L_1c_{4z}\\
L_2c_{1z}&L_2c_{2z}&L_2c_{3z}&L_2c_{4z}\\
L_3c_{1z}&L_3c_{2z}&L_3c_{3z}&L_3c_{4z}\\
L_4c_{1z}&L_4c_{2z}&L_4c_{3z}&L_4c_{4z}
\end{bmatrix}dV\{\Theta\}
\end{aligned}
\]
伝導伝熱の項
\[
\begin{aligned}
&+\frac{1}{Pe}\int_V\frac{1}{36V^2}
\begin{bmatrix}
c_{1x}c_{1x}&c_{1x}c_{2x}&c_{1x}c_{3x}&c_{1x}c_{4x}\\
c_{2x}c_{1x}&c_{2x}c_{2x}&c_{2x}c_{3x}&c_{2x}c_{4x}\\
c_{3x}c_{1x}&c_{3x}c_{2x}&c_{3x}c_{3x}&c_{3x}c_{4x}\\
c_{4x}c_{1x}&c_{4x}c_{2x}&c_{4x}c_{3x}&c_{4x}c_{4x}
\end{bmatrix}dV\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\int_V\frac{1}{36V^2}
\begin{bmatrix}
c_{1y}c_{1y}&c_{1y}c_{2y}&c_{1y}c_{3y}&c_{1y}c_{4y}\\
c_{2y}c_{1y}&c_{2y}c_{2y}&c_{2y}c_{3y}&c_{2y}c_{4y}\\
c_{3y}c_{1y}&c_{3y}c_{2y}&c_{3y}c_{3y}&c_{3y}c_{4y}\\
c_{4y}c_{1y}&c_{4y}c_{2y}&c_{4y}c_{3y}&c_{4y}c_{4y}
\end{bmatrix}dV\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\int_V\frac{1}{36V^2}
\begin{bmatrix}
c_{1z}c_{1z}&c_{1z}c_{2z}&c_{1z}c_{3z}&c_{1z}c_{4z}\\
c_{2z}c_{1z}&c_{2z}c_{2z}&c_{2z}c_{3z}&c_{2z}c_{4z}\\
c_{3z}c_{1z}&c_{3z}c_{2z}&c_{3z}c_{3z}&c_{3z}c_{4z}\\
c_{4z}c_{1z}&c_{4z}c_{2z}&c_{4z}c_{3z}&c_{4z}c_{4z}
\end{bmatrix}dV\{\Theta\}
\end{aligned}
\]
対流伝熱の項
\[
+Nu(\Theta-\Theta_h)\int_S
\begin{bmatrix}
L_1\\L_2\\L_3
\end{bmatrix}dS
\]
ここで、面積積分、体積積分の公式より
\[
\begin{aligned}
\int_V L_1^pL_2^qL_3^rL_4^s\,dV
&=\frac{p!q!r!s!}{(p+q+r+s+3)!}\,6V\\[6pt]
\int_V L_iL_j\,dV
&=
\begin{cases}
\displaystyle\frac{1!1!}{(1+1+3)!}\,6V
=\frac{6}{5!}V
=\frac{1}{20}V &(i\ne j)\\
\displaystyle\frac{2!}{(1+1+3)!}\,6V
=\frac{12}{5!}V
=\frac{1}{10}V &(i=j)
\end{cases}\\[6pt]
\int_V L_i\,dV
&=\frac{1!}{(1+3)!}\,6V
=\frac{6}{4!}V
=\frac{1}{4}V\\[6pt]
\int_S L_1^pL_2^qL_3^r\,dS
&=\frac{p!q!r!}{(p+q+r+2)!}\,2S\\[6pt]
\int_S L_i\,dS
&=\frac{1}{(1+2)!}\,2S
=\frac{1}{3}S
\end{aligned}
\]
形状関数を積分すると
\[
=
\frac{1}{20}V
\begin{bmatrix}
2&1&1&1\\
1&2&1&1\\
1&1&2&1\\
1&1&1&2
\end{bmatrix}
\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}
{\Delta\tau}
\]
対流項
\[
\begin{aligned}
&+V_x\frac{1}{6V}\frac{V}{4}
\begin{bmatrix}
c_{1x}&c_{2x}&c_{3x}&c_{4x}\\
c_{1x}&c_{2x}&c_{3x}&c_{4x}\\
c_{1x}&c_{2x}&c_{3x}&c_{4x}\\
c_{1x}&c_{2x}&c_{3x}&c_{4x}
\end{bmatrix}\{\Theta\}\\[6pt]
&+V_y\frac{1}{6V}\frac{V}{4}
\begin{bmatrix}
c_{1y}&c_{2y}&c_{3y}&c_{4y}\\
c_{1y}&c_{2y}&c_{3y}&c_{4y}\\
c_{1y}&c_{2y}&c_{3y}&c_{4y}\\
c_{1y}&c_{2y}&c_{3y}&c_{4y}
\end{bmatrix}\{\Theta\}\\[6pt]
&+V_z\frac{1}{6V}\frac{V}{4}
\begin{bmatrix}
c_{1z}&c_{2z}&c_{3z}&c_{4z}\\
c_{1z}&c_{2z}&c_{3z}&c_{4z}\\
c_{1z}&c_{2z}&c_{3z}&c_{4z}\\
c_{1z}&c_{2z}&c_{3z}&c_{4z}
\end{bmatrix}\{\Theta\}
\end{aligned}
\]
伝導伝熱の項
\[
\begin{aligned}
&+\frac{1}{Pe}\frac{1}{36V^2}V
\begin{bmatrix}
c_{1x}c_{1x}&c_{1x}c_{2x}&c_{1x}c_{3x}&c_{1x}c_{4x}\\
c_{2x}c_{1x}&c_{2x}c_{2x}&c_{2x}c_{3x}&c_{2x}c_{4x}\\
c_{3x}c_{1x}&c_{3x}c_{2x}&c_{3x}c_{3x}&c_{3x}c_{4x}\\
c_{4x}c_{1x}&c_{4x}c_{2x}&c_{4x}c_{3x}&c_{4x}c_{4x}
\end{bmatrix}\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\frac{1}{36V^2}V
\begin{bmatrix}
c_{1y}c_{1y}&c_{1y}c_{2y}&c_{1y}c_{3y}&c_{1y}c_{4y}\\
c_{2y}c_{1y}&c_{2y}c_{2y}&c_{2y}c_{3y}&c_{2y}c_{4y}\\
c_{3y}c_{1y}&c_{3y}c_{2y}&c_{3y}c_{3y}&c_{3y}c_{4y}\\
c_{4y}c_{1y}&c_{4y}c_{2y}&c_{4y}c_{3y}&c_{4y}c_{4y}
\end{bmatrix}\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\frac{1}{36V^2}V
\begin{bmatrix}
c_{1z}c_{1z}&c_{1z}c_{2z}&c_{1z}c_{3z}&c_{1z}c_{4z}\\
c_{2z}c_{1z}&c_{2z}c_{2z}&c_{2z}c_{3z}&c_{2z}c_{4z}\\
c_{3z}c_{1z}&c_{3z}c_{2z}&c_{3z}c_{3z}&c_{3z}c_{4z}\\
c_{4z}c_{1z}&c_{4z}c_{2z}&c_{4z}c_{3z}&c_{4z}c_{4z}
\end{bmatrix}\{\Theta\}
\end{aligned}
\]
対流伝熱の項
\[
+Nu(\Theta-\Theta_h)\frac{S}{3}
\begin{bmatrix}
1\\1\\1
\end{bmatrix}
\]
係数をまとめて
\[
\begin{aligned}
&+V_x\frac{1}{24}
\begin{bmatrix}
c_{1x}&c_{2x}&c_{3x}&c_{4x}\\
c_{1x}&c_{2x}&c_{3x}&c_{4x}\\
c_{1x}&c_{2x}&c_{3x}&c_{4x}\\
c_{1x}&c_{2x}&c_{3x}&c_{4x}
\end{bmatrix}\{\Theta\}\\[6pt]
&+V_y\frac{1}{24}
\begin{bmatrix}
c_{1y}&c_{2y}&c_{3y}&c_{4y}\\
c_{1y}&c_{2y}&c_{3y}&c_{4y}\\
c_{1y}&c_{2y}&c_{3y}&c_{4y}\\
c_{1y}&c_{2y}&c_{3y}&c_{4y}
\end{bmatrix}\{\Theta\}\\[6pt]
&+V_z\frac{1}{24}
\begin{bmatrix}
c_{1z}&c_{2z}&c_{3z}&c_{4z}\\
c_{1z}&c_{2z}&c_{3z}&c_{4z}\\
c_{1z}&c_{2z}&c_{3z}&c_{4z}\\
c_{1z}&c_{2z}&c_{3z}&c_{4z}
\end{bmatrix}\{\Theta\}
\end{aligned}
\]
対流項
\[
\begin{aligned}
&+\frac{1}{Pe}\frac{1}{36V}
\begin{bmatrix}
c_{1x}c_{1x}&c_{1x}c_{2x}&c_{1x}c_{3x}&c_{1x}c_{4x}\\
c_{2x}c_{1x}&c_{2x}c_{2x}&c_{2x}c_{3x}&c_{2x}c_{4x}\\
c_{3x}c_{1x}&c_{3x}c_{2x}&c_{3x}c_{3x}&c_{3x}c_{4x}\\
c_{4x}c_{1x}&c_{4x}c_{2x}&c_{4x}c_{3x}&c_{4x}c_{4x}
\end{bmatrix}\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\frac{1}{36V}
\begin{bmatrix}
c_{1y}c_{1y}&c_{1y}c_{2y}&c_{1y}c_{3y}&c_{1y}c_{4y}\\
c_{2y}c_{1y}&c_{2y}c_{2y}&c_{2y}c_{3y}&c_{2y}c_{4y}\\
c_{3y}c_{1y}&c_{3y}c_{2y}&c_{3y}c_{3y}&c_{3y}c_{4y}\\
c_{4y}c_{1y}&c_{4y}c_{2y}&c_{4y}c_{3y}&c_{4y}c_{4y}
\end{bmatrix}\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\frac{1}{36V}
\begin{bmatrix}
c_{1z}c_{1z}&c_{1z}c_{2z}&c_{1z}c_{3z}&c_{1z}c_{4z}\\
c_{2z}c_{1z}&c_{2z}c_{2z}&c_{2z}c_{3z}&c_{2z}c_{4z}\\
c_{3z}c_{1z}&c_{3z}c_{2z}&c_{3z}c_{3z}&c_{3z}c_{4z}\\
c_{4z}c_{1z}&c_{4z}c_{2z}&c_{4z}c_{3z}&c_{4z}c_{4z}
\end{bmatrix}\{\Theta\}
\end{aligned}
\]
伝導伝熱の項
\[
+Nu(\Theta-\Theta_h)\frac{S}{3}
\begin{bmatrix}
1\\1\\1
\end{bmatrix}
\]
対流伝熱の項
\[
\begin{aligned}
&={}
[C]\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}{\Delta\tau}\\[6pt]
&+V_x[C_x]\{\Theta\}
+V_y[C_y]\{\Theta\}
+V_z[C_z]\{\Theta\}\\[6pt]
&+\frac{1}{Pe}[S_{xx}]\{\Theta\}
+\frac{1}{Pe}[S_{yy}]\{\Theta\}
+\frac{1}{Pe}[S_{zz}]\{\Theta\}\\[6pt]
&+Nu(\Theta-\Theta_h)\frac{S}{3}
\begin{bmatrix}1\\1\\1\end{bmatrix}
\end{aligned}
\]
行列式をまとめると
\[
\begin{aligned}
&={}
[C]\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}{\Delta\tau}\\[6pt]
&+\left(V_x[C_x]+V_y[C_y]+V_z[C_z]\right)\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\left([S_{xx}]+[S_{yy}]+[S_{zz}]\right)\{\Theta\}\\[6pt]
&+Nu(\Theta-\Theta_h)\frac{S}{3}
\begin{bmatrix}1\\1\\1\end{bmatrix}\\[6pt]
&={}
\begin{bmatrix}0\\0\\0\\0\end{bmatrix}
\end{aligned}
\]
最終的に次式が導出されます。
\[
\begin{aligned}
&[C]\frac{\{\Theta\}^{\tau+\Delta\tau}-\{\Theta\}^{\tau}}{\Delta\tau}\\[6pt]
&+\left(V_x[C_x]+V_y[C_y]+V_z[C_z]\right)\{\Theta\}\\[6pt]
&+\frac{1}{Pe}\left([S_{xx}]+[S_{yy}]+[S_{zz}]\right)\{\Theta\}\\[6pt]
&+Nu(\Theta-\Theta_h)\frac{S}{3}
\begin{bmatrix}1\\1\\1\end{bmatrix}
=
\begin{bmatrix}0\\0\\0\\0\end{bmatrix}
\end{aligned}
\]
既知の項を右辺に移項します。下式は陰解法の場合の離散化式になります。
\[
\begin{aligned}
&\frac{[C]}{\Delta\tau}\{\Theta\}^{\tau+\Delta\tau}
+\left(V_x[C_x]+V_y[C_y]+V_z[C_z]\right)\{\Theta\}^{\tau+\Delta\tau}\\[6pt]
&+\frac{1}{Pe}\left([S_{xx}]+[S_{yy}]+[S_{zz}]\right)\{\Theta\}^{\tau+\Delta\tau}\\[6pt]
&={}
\frac{[C]}{\Delta\tau}\{\Theta\}^{\tau}
-Nu(\Theta-\Theta_h)\frac{S}{3}
\begin{bmatrix}1\\1\\1\end{bmatrix}
\end{aligned}
\]
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