diff --git a/olaflow/processing/olaflow.py b/olaflow/processing/olaflow.py
new file mode 100644
index 0000000..9556a84
--- /dev/null
+++ b/olaflow/processing/olaflow.py
@@ -0,0 +1,21 @@
+import re
+
+
+class OFModel:
+    def __init__(self, root):
+        self._root = root
+
+    def write_field(self, field, values):
+        with open(self._root.joinpath("0", field), "r") as aw_file:
+            aw_raw = aw_file.read()
+
+        with open(self._root.joinpath("0", field), "w") as aw_file:
+            aw_file.write(
+                re.sub(
+                    r"(?<=\(\n).*?(?=\n\))",
+                    "\n".join(values.astype(str)),
+                    aw_raw,
+                    count=1,
+                    flags=re.S,
+                )
+            )
diff --git a/olaflow/processing/sws_ola.py b/olaflow/processing/sws_ola.py
index 0eb4ddb..97940ec 100644
--- a/olaflow/processing/sws_ola.py
+++ b/olaflow/processing/sws_ola.py
@@ -9,6 +9,8 @@ import numpy as np
 from fluidfoam import readof
 from scipy import interpolate
 
+from .olaflow import OFModel
+
 parser = argparse.ArgumentParser(
     description="Convert swash output to olaFlow input"
 )
@@ -32,18 +34,7 @@ of_x, of_y, of_z = mesh = readof.readmesh(str(olaflow_root))
 
 watl = interpolate.interp1d(x, sws["watl"][680])
 
-alpha_water = np.where(of_z < watl(of_x), "1", "0")
+alpha_water = np.where(of_z < watl(of_x), 1, 0)
 
-with open(olaflow_root.joinpath("0", "alpha.water"), "r") as aw_file:
-    aw_raw = aw_file.read()
-
-with open(olaflow_root.joinpath("0", "alpha.water"), "w") as aw_file:
-    aw_file.write(
-        re.sub(
-            r"(?<=\(\n).*?(?=\n\))",
-            "\n".join(alpha_water),
-            aw_raw,
-            count=1,
-            flags=re.S,
-        )
-    )
+model = OFModel(olaflow_root)
+model.write_field("alpha.water", alpha_water)