I updated movement.py with an IncrementalMovement class.

pterasoftware/movement.py

@@ -16,6 +16,9 @@
     OperatingPointMovement: This is a class used to contain the movement
     characteristics of an operating point.
 
+    IncrementalMovement: This is a class used to contain the movement characteristics of an unsteady
+    aerodynamics problem with incremental (non-precomputed) motion.
+
 This module contains the following exceptions:
     None
 
@@ -1483,3 +1486,75 @@ def oscillating_customspace(
 
     # Calculate and return the values.
     return a * custom_function(b * (times - h)) + k
+
+
+class IncrementalMovement:
+    """This is a class used to contain the movement characteristics of an unsteady
+    aerodynamics problem with incremental (non-precomputed) motion.
+
+    This class contains the following public methods:
+        None
+
+    This class contains the following class attributes:
+        None
+
+    Subclassing:
+        This class is not meant to be subclassed.
+    """
+
+    def __init__(
+        self,
+        initial_airplanes,
+        initial_operating_point,
+        delta_time=None,
+    ):
+        """This is the initialization method.
+
+        :param initial_airplanes: list of Airplane objects
+            This is a list of objects which characterize the initial position of each airplane in the problem.
+        :param initial_operating_point: OperatingPoint
+            This parameter is the problem's initial operating point.
+        :param delta_time: float, optional
+            This float is the time, in seconds, between each time step. If
+            not given a value, this method will calculate one such the ring vortices
+            shed off the main wing will have roughly the same chord length as the
+            panels on the main wing. This is based on the initial airplane's reference
+            chord length, its main wing's number of chordwise panels, and its base
+            operating point's velocity (in the case of multiple airplanes, delta_time is the average of each airplane's calculated ideal value).
+        """
+
+        # Initialize the class attributes.
+        self.initial_airplanes = initial_airplanes
+        self.initial_operating_point = initial_operating_point
+
+        # Calculate default delta_time value if the user hasn't passed one in.
+        if delta_time is None:
+            delta_times = []
+            for initial_airplane in self.initial_airplanes:
+
+                # For a given airplane object, the ideal time step length is that
+                # which sheds ring vortices off the main wing that have roughly the
+                # same chord length as the panels on the main wing. This is based on
+                # the airplane's reference chord length, its main wing's number
+                # of chordwise panels, and its base operating point's velocity.
+                delta_times.append(
+                    initial_airplane.c_ref
+                    / initial_airplane.wings[0].num_chordwise_panels
+                    / self.initial_operating_point.velocity
+                )
+
+            # Set the delta time to be the average of the airplanes' ideal delta times.
+            delta_time = sum(delta_times) / len(delta_times)
+
+        self.delta_time = delta_time
+
+        # Generate what will become a list of lists of airplane objects that are the steps through the
+        # movement of each of this problem's base airplanes. The first index
+        # identifies the base airplane and the second index identifies the time step. For now, add each base airplane to the list for the initial time step.
+        self.airplanes = []
+        for initial_airplane in self.initial_airplanes:
+            self.airplanes.append([initial_airplane])
+
+        # Generate what will become a list of operating point objects that are the steps through the
+        # movement of this problem's operating point. For now, add base operating point, which corresponds to the first time step.
+        self.operating_points = [initial_operating_point]