From 8f973136e049991867aa202c9d7d2b179aecaf13 Mon Sep 17 00:00:00 2001
From: Phil Elson <philip.elson@cern.ch>
Date: Mon, 9 Nov 2020 09:40:11 +0100
Subject: [PATCH] Allow WindowOpening to have more than one window of the given
 dimensions.

---
 cara/apps/calculator/model_generator.py       | 19 ++++++------
 .../templates/calculator.form.html.j2         |  2 +-
 cara/models.py                                | 31 +++++++++++++------
 cara/tests/test_ventilation.py                | 25 +++++++++++++++
 4 files changed, 56 insertions(+), 21 deletions(-)
 create mode 100644 cara/tests/test_ventilation.py

diff --git a/cara/apps/calculator/model_generator.py b/cara/apps/calculator/model_generator.py
index ef4e74fa..71ac9acd 100644
--- a/cara/apps/calculator/model_generator.py
+++ b/cara/apps/calculator/model_generator.py
@@ -120,12 +120,9 @@ class FormData:
         # Initializes a ventilation instance as a window if 'natural' is selected, or as a HEPA-filter otherwise
         if self.ventilation_type == 'natural':
             if self.windows_open == 'interval':
-                period, duration = 120, 10
-            elif self.windows_number == 'breaks':
-                # TODO: Implement windows open in breaks
-                period, duration = 120, 120
+                window_interval = models.PeriodicInterval(120, 10)
             else:
-                period, duration = 120, 120
+                window_interval = always_on
 
             if self.event_type == 'single_event':
                 month_number = int(self.single_event_date.split('/')[1])
@@ -136,11 +133,13 @@ class FormData:
             inside_temp = models.PiecewiseConstant((0, 24), (293,))
             outside_temp = models.GenevaTemperatures[month]
 
-            # I multiply the opening width by the number of windows to simulate the correct window area
-            ventilation = models.WindowOpening(active=models.PeriodicInterval(period=period, duration=duration),
-                                               inside_temp=inside_temp, outside_temp=outside_temp, cd_b=0.6,
-                                               window_height=self.window_height,
-                                               opening_length=self.opening_distance * self.windows_number)
+            ventilation = models.WindowOpening(
+                active=window_interval,
+                inside_temp=inside_temp, outside_temp=outside_temp, cd_b=0.6,
+                window_height=self.window_height,
+                opening_length=self.opening_distance,
+                number_of_windows=self.windows_number,
+            )
         elif self.ventilation_type == "no-ventilation":
             ventilation = models.AirChange(active=always_on, air_exch=0.)
         else:
diff --git a/cara/apps/calculator/templates/calculator.form.html.j2 b/cara/apps/calculator/templates/calculator.form.html.j2
index df4ccb91..74f3c3f7 100644
--- a/cara/apps/calculator/templates/calculator.form.html.j2
+++ b/cara/apps/calculator/templates/calculator.form.html.j2
@@ -51,7 +51,7 @@ Beta v1.0.0 <span style="float:right; font-weight:bold">Please send feedback to
     </div>
 
     <div id="DIVnatural_ventilation" style="display:none">
-        Number of windows: <input type="number" id="windows_number" name="windows_number" min="0"><br>
+        Number of windows: <input type="number" id="windows_number" name="windows_number" min="1"><br>
         Height of window: <input type="number" step=0.01 id="window_height" name="window_height" placeholder="meters" min="0"><br>
         Width of window: <input type="number" step=0.01 id="window_width"  name="window_width" placeholder="meters" min="0"><br>
         Opening distance: <input type="number" step=0.01 id="opening_distance"  name="opening_distance" placeholder="meters" min="0"><br>
diff --git a/cara/models.py b/cara/models.py
index 7737bd2d..33776079 100644
--- a/cara/models.py
+++ b/cara/models.py
@@ -208,14 +208,24 @@ class WindowOpening(Ventilation):
     #: The interval in which the window is open.
     active: Interval
 
-    inside_temp: PiecewiseConstant   #: The temperature inside the room (Kelvin)
-    outside_temp: PiecewiseConstant   #: The temperature outside of the window (Kelvin)
+    #: The temperature inside the room (Kelvin).
+    inside_temp: PiecewiseConstant
 
-    window_height: float   #: The height of the window
+    #: The temperature outside of the window (Kelvin).
+    outside_temp: PiecewiseConstant
 
-    opening_length: float   #: The length of the opening-gap when the window is open
+    #: The height of the window.
+    window_height: float
 
-    cd_b: float = 0.6   #: Discharge coefficient: what portion effective area is used to exchange air (0 <= cd_b <= 1)
+    #: The length of the opening-gap when the window is open
+    opening_length: float
+
+    #: The number of windows of the given dimensions.
+    number_of_windows: int = 1
+
+    #: Discharge coefficient: what portion effective area is
+    #: used to exchange air (0 <= cd_b <= 1)
+    cd_b: float = 0.6
 
     def transition_times(self) -> typing.Set[float]:
         transitions = super().transition_times()
@@ -228,13 +238,14 @@ class WindowOpening(Ventilation):
         if not self.active.triggered(time):
             return 0.
 
+        inside_temp = self.inside_temp.value(time)
+        outside_temp = self.outside_temp.value(time)
+
         # Reminder, no dependence on time in the resulting calculation.
-
-        temp_delta = abs(self.inside_temp.value(time) - 
-                self.outside_temp.value(time)) / self.outside_temp.value(time)
+        temp_delta = abs(inside_temp - outside_temp) / outside_temp
         root = np.sqrt(9.81 * self.window_height * temp_delta)
-
-        return (3600 / (3 * room.volume)) * self.cd_b * self.window_height * self.opening_length * root
+        window_area = self.window_height * self.opening_length * self.number_of_windows
+        return (3600 / (3 * room.volume)) * self.cd_b * window_area * root
 
 
 @dataclass(frozen=True)
diff --git a/cara/tests/test_ventilation.py b/cara/tests/test_ventilation.py
new file mode 100644
index 00000000..aaf64983
--- /dev/null
+++ b/cara/tests/test_ventilation.py
@@ -0,0 +1,25 @@
+import dataclasses
+
+import pytest
+
+from cara import models
+
+
+@pytest.fixture
+def baseline_window():
+    return models.WindowOpening(
+            active=models.SpecificInterval(((0, 4), (5, 9))),
+            inside_temp=models.PiecewiseConstant((0, 24), (293,)),
+            outside_temp=models.PiecewiseConstant((0, 24), (283,)),
+            cd_b=0.6, window_height=1.6, opening_length=0.6,
+        )
+
+
+def test_number_of_windows(baseline_window):
+    room = models.Room(75)
+    two_windows = dataclasses.replace(baseline_window, number_of_windows=2)
+
+    one_window_exchange = baseline_window.air_exchange(room, 1)
+    two_window_exchange = two_windows.air_exchange(room, 1)
+    assert one_window_exchange != 0
+    assert one_window_exchange * 2 == two_window_exchange