144 lines
3.8 KiB
Rust
144 lines
3.8 KiB
Rust
//! 短特征辐射转移求解器
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//!
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//! 原始 Fortran: rte_sc.f
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//! Short Characteristics 方法求解辐射转移方程
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/// 短特征辐射转移求解器
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///
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/// 对已知源函数的辐射转移方程进行形式求解
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///
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/// # 参数
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/// - `dtau`: 光学深度增量 (nd-1 个元素)
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/// - `st0`: 总源函数 (nd 个元素)
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/// - `rup`: 上边界强度 (id=1)
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/// - `rdown`: 下边界强度 (id=nd)
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/// - `amu0`: 传播角度余弦 (相对于法线)
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/// - amu0 < 0: 入射辐射 (向下)
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/// - amu0 >= 0: 出射辐射 (向上)
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/// - `ri`: 辐射强度 (输出)
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/// - `ali`: Lambda 算子对角元素 (输出)
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/// - `nd`: 深度点数
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///
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/// # 算法
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/// 使用短特征 (Short Characteristics) 方法
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pub fn rte_sc(
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dtau: &[f64],
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st0: &[f64],
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rup: f64,
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rdown: f64,
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amu0: f64,
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ri: &mut [f64],
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ali: &mut [f64],
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nd: usize,
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) {
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// 工作数组
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let mut dtx1 = vec![0.0; nd];
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let mut dtx2 = vec![0.0; nd];
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let mut dtx0 = vec![0.0; nd];
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// 常量
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let un = 1.0_f64;
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// 预计算指数因子
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for id in 0..nd - 1 {
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dtx1[id] = (-dtau[id]).exp();
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dtx2[id] = (un - dtx1[id]) / dtau[id];
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dtx0[id] = un - dtx2[id];
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}
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// 入射强度 (向下传播)
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if amu0 < 0.0 {
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let id = 0;
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ri[id] = rup;
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for id in 0..nd - 1 {
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ri[id + 1] = ri[id] * dtx1[id]
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+ st0[id] * (dtx2[id] - dtx1[id])
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+ st0[id + 1] * dtx0[id];
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ali[id + 1] = dtx0[id];
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}
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ali[0] = 0.0;
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} else {
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// 出射强度 (向上传播)
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ri[nd - 1] = rdown;
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for id in (0..nd - 1).rev() {
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ri[id] = ri[id + 1] * dtx1[id]
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+ st0[id] * dtx0[id]
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+ st0[id + 1] * (dtx2[id] - dtx1[id]);
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ali[id] = dtx0[id];
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}
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ali[nd - 1] = 0.0;
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_rte_sc_incoming() {
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// 测试入射辐射
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let nd = 5;
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let dtau = vec![0.5; nd - 1];
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let st0 = vec![1.0; nd];
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let rup = 0.0;
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let rdown = 0.0;
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let amu0 = -1.0; // 入射
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let mut ri = vec![0.0; nd];
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let mut ali = vec![0.0; nd];
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rte_sc(&dtau, &st0, rup, rdown, amu0, &mut ri, &mut ali, nd);
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// 入射边界条件
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assert!((ri[0] - 0.0).abs() < 1e-10);
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assert!((ali[0] - 0.0).abs() < 1e-10);
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// 强度应该随深度增加
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assert!(ri[nd - 1] > ri[0]);
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}
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#[test]
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fn test_rte_sc_outgoing() {
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// 测试出射辐射
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let nd = 5;
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let dtau = vec![0.5; nd - 1];
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let st0 = vec![1.0; nd];
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let rup = 0.0;
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let rdown = 0.0;
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let amu0 = 1.0; // 出射
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let mut ri = vec![0.0; nd];
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let mut ali = vec![0.0; nd];
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rte_sc(&dtau, &st0, rup, rdown, amu0, &mut ri, &mut ali, nd);
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// 出射边界条件
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assert!((ri[nd - 1] - 0.0).abs() < 1e-10);
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assert!((ali[nd - 1] - 0.0).abs() < 1e-10);
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// 强度应该随深度增加
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assert!(ri[0] > ri[nd - 1]);
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}
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#[test]
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fn test_rte_sc_consistency() {
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// 测试源函数为常数时的渐进行为
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let nd = 100;
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let dtau = vec![0.1; nd - 1];
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let st0 = vec![2.0; nd];
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let rup = 0.0;
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let rdown = 0.0;
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let mut ri_in = vec![0.0; nd];
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let mut ali_in = vec![0.0; nd];
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let mut ri_out = vec![0.0; nd];
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let mut ali_out = vec![0.0; nd];
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rte_sc(&dtau, &st0, rup, rdown, -1.0, &mut ri_in, &mut ali_in, nd);
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rte_sc(&dtau, &st0, rup, rdown, 1.0, &mut ri_out, &mut ali_out, nd);
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// 在深部，入射和出射强度应趋近于源函数
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// (对于光学厚介质)
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assert!((ri_in[nd - 1] - st0[nd - 1]).abs() < 0.1);
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assert!((ri_out[0] - st0[0]).abs() < 0.1);
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}
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}
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