From f7970f9b769369220ed3c607a27081b8ea93e409 Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Sat, 1 Mar 2025 18:53:29 -0500
Subject: add pressure ratio output

---
 engine.c | 15 +++++++++++++++
 engine.h |  2 ++
 main.c   | 16 ++++++++++++++++
 ui.c     | 19 +++++++++++++++++++
 ui.h     |  2 ++
 5 files changed, 54 insertions(+)

diff --git a/engine.c b/engine.c
index 1817180..5c1568d 100644
--- a/engine.c
+++ b/engine.c
@@ -13,6 +13,21 @@ init_engine(Engine *e) {
 	memset(e, 0, sizeof(*e));
 }
 
+/* Pressure ratio across the compressor. */
+double
+pressure_ratio(const Engine *e) {
+	Pressure p1, p2;
+
+	p1 = e->ambient_pressure;
+	p2 = comp_outlet_pressure(e);
+	return p2 / p1;
+}
+
+Pressure
+comp_outlet_pressure(const Engine *e) {
+	return e->map + e->intercooler_deltap;
+}
+
 VolumeFlowRate
 volume_flow_rate(const Engine *e) {
 	double n = as_rpm(e->rpm);
diff --git a/engine.h b/engine.h
index 89c6a13..7e1eb1e 100644
--- a/engine.h
+++ b/engine.h
@@ -11,4 +11,6 @@ typedef struct {
 } Engine;
 
 void init_engine(Engine *e);
+Pressure comp_outlet_pressure(const Engine *e);
+double pressure_ratio(const Engine *e);
 VolumeFlowRate volume_flow_rate(const Engine *e);
diff --git a/main.c b/main.c
index 8242853..4faa1de 100644
--- a/main.c
+++ b/main.c
@@ -66,6 +66,7 @@ static void comp_efficiency_row(mu_Context *ctx, UI *ui);
 static void intercooler_efficiency_row(mu_Context *ctx, UI *ui);
 static void intercooler_deltap_row(mu_Context *ctx, UI *ui);
 static void dup_del_row(mu_Context *ctx, UI *ui);
+static void pressure_ratio_row(mu_Context *ctx, UI *ui);
 static void volume_flow_rate_row(mu_Context *ctx, UI *ui);
 static void hpad(mu_Context *ctx, int w);
 static void vpad(mu_Context *ctx, int h);
@@ -149,6 +150,7 @@ main_window(mu_Context *ctx, UI *ui) {
 
 	vpad(ctx, 0);
 
+	pressure_ratio_row(ctx, ui);
 	volume_flow_rate_row(ctx, ui);
 
 	mu_end_window(ctx);
@@ -325,6 +327,20 @@ dup_del_row(mu_Context *ctx, UI *ui) {
 	}
 }
 
+static void
+pressure_ratio_row(mu_Context *ctx, UI *ui) {
+	int i;
+
+	mu_layout_row(ctx, 0, NULL, 0);
+	mu_layout_width(ctx, LABEL_WIDTH);
+	mu_label(ctx, "Pressure ratio:");
+	hpad(ctx, UNIT_WIDTH);
+	mu_layout_width(ctx, FIELD_WIDTH);
+	for (i = 0; i < ui->npoints; i++) {
+		w_number(ctx, ui->pressure_ratio[i]);
+	}
+}
+
 static void
 volume_flow_rate_row(mu_Context *ctx, UI *ui) {
 	int i;
diff --git a/ui.c b/ui.c
index 0aeaae8..b8d959d 100644
--- a/ui.c
+++ b/ui.c
@@ -60,7 +60,9 @@ static void init_ve(UI *ui);
 static void init_comp_efficiency(UI *ui);
 static void init_intercooler_efficiency(UI *ui);
 static void init_intercooler_deltap(UI *ui);
+static void init_pressure_ratio(UI *ui);
 static void init_volume_flow_rate(UI *ui);
+static void compute_pressure_ratio(UI *ui, int idx);
 static void compute_volume_flow_rate(UI *ui, int idx);
 
 
@@ -80,6 +82,7 @@ init_ui(UI *ui) {
 	init_intercooler_efficiency(ui);
 	init_intercooler_deltap(ui);
 
+	init_pressure_ratio(ui);
 	init_volume_flow_rate(ui);
 
 	compute(ui, 0);
@@ -187,6 +190,11 @@ init_intercooler_deltap(UI *ui) {
 	set_intercooler_deltap(ui, 0);
 }
 
+static void
+init_pressure_ratio(UI *ui) {
+	w_init_number(ui->pressure_ratio[0]);
+}
+
 static void
 init_volume_flow_rate(UI *ui) {
 	w_init_select(&ui->volume_flow_rate_unit, nelem(volume_flow_rate_units), volume_flow_rate_units);
@@ -360,6 +368,7 @@ set_intercooler_deltap_unit(UI *ui) {
 
 void
 compute(UI *ui, int idx) {
+	compute_pressure_ratio(ui, idx);
 	compute_volume_flow_rate(ui, idx);
 }
 
@@ -372,6 +381,14 @@ compute_all(UI *ui) {
 	}
 }
 
+static void
+compute_pressure_ratio(UI *ui, int idx) {
+	double pr;
+
+	pr = pressure_ratio(&ui->points[idx]);
+	w_set_number(ui->pressure_ratio[idx], pr);
+}
+
 static void
 compute_volume_flow_rate(UI *ui, int idx) {
 	int unit_idx;
@@ -404,6 +421,7 @@ insert_point(UI *ui, int idx) {
 		memmove(&ui->intercooler_efficiency[i], &ui->intercooler_efficiency[i-1], sizeof(ui->intercooler_efficiency[i-1]));
 		memmove(&ui->intercooler_deltap[i], &ui->intercooler_deltap[i-1], sizeof(ui->intercooler_deltap[i-1]));
 
+		memmove(&ui->pressure_ratio[i], &ui->pressure_ratio[i-1], sizeof(ui->pressure_ratio[i-1]));
 		memmove(&ui->volume_flow_rate[i], &ui->volume_flow_rate[i-1], sizeof(ui->volume_flow_rate[i-1]));
 	}
 	ui->npoints++;
@@ -425,6 +443,7 @@ remove_point(UI *ui, int idx) {
 		memmove(&ui->intercooler_efficiency[idx], &ui->intercooler_efficiency[idx+1], sizeof(ui->intercooler_efficiency[idx]));
 		memmove(&ui->intercooler_deltap[idx], &ui->intercooler_deltap[idx+1], sizeof(ui->intercooler_deltap[idx]));
 
+		memmove(&ui->pressure_ratio[idx], &ui->pressure_ratio[idx+1], sizeof(ui->pressure_ratio[idx]));
 		memmove(&ui->volume_flow_rate[idx], &ui->volume_flow_rate[idx+1], sizeof(ui->volume_flow_rate[idx]));
 	}
 	ui->npoints--;
diff --git a/ui.h b/ui.h
index bd00b68..c83dff8 100644
--- a/ui.h
+++ b/ui.h
@@ -27,6 +27,8 @@ typedef struct {
 	w_Field intercooler_deltap[MAX_POINTS];
 	w_Select intercooler_deltap_unit;
 
+	w_Number pressure_ratio[MAX_POINTS];
+
 	w_Select volume_flow_rate_unit;
 	w_Number volume_flow_rate[MAX_POINTS];
 } UI;
-- 
cgit v1.2.3