Initial commit: GasFlux project with core processing pipelines

src/gasflux/gas.py

@@ -0,0 +1,58 @@
+"""functions related to gas transformations and calculations, e.g. density, point flux etc."""
+
+import molmass
+import pandas as pd
+
+gas_variables = {
+    "standard_pressure": 1013.25,  # hPa/mbar
+    "standard_temperature": 273.15,  # degrees K
+    "standard_molar_volume": 0.022413969545014,  # m3⋅mol-1
+}
+
+
+def mass(formula: str) -> float:
+    """Return the molar mass of a gas in g/mol."""
+    return molmass.Formula(formula.upper()).mass  # only accepts capital letters
+
+
+def gas_density(local_pressure: float, local_temperature_celsius: float, gas: str) -> float:  # millibars and celsius
+    """
+    Calculate the density of a gas in kg/m3 based on local pressure and temperature.
+
+    Parameters:
+    - local_pressure: The local pressure in hPa/mbar.
+    - local_temperature: The local temperature in degrees Celsius.
+    - gas: The chemical formula of the gas.
+
+    Returns:
+    - The density of the gas in kg/m3.
+
+    Assumes ideal gas behavior.
+    """
+    local_temperature_kelvin = local_temperature_celsius + gas_variables["standard_temperature"]
+    local_volume = (
+        gas_variables["standard_molar_volume"]
+        * (gas_variables["standard_pressure"] / local_pressure)
+        * ((local_temperature_kelvin + gas_variables["standard_temperature"]) / gas_variables["standard_temperature"])
+    )  # m3⋅mol-1
+    return mass(gas) / 1000 / local_volume
+
+
+def gas_flux_column(df: pd.DataFrame, gas: str, wind: str = "windspeed") -> pd.DataFrame:
+    """
+    Add columns to the DataFrame for the gas density, mass, and flux.
+
+    Parameters:
+    - df: The DataFrame.
+    - gas: The chemical formula of the gas.
+    - wind: The column name for the wind speed (NB - must be perpendicular to the plane)
+
+    Returns:
+    - The DataFrame with the added columns.
+    """
+    average_temp = df["temperature"].mean()  # celsius
+    average_pressure = df["pressure"].mean()  # hPa
+    gd = gas_density(local_pressure=average_pressure, local_temperature_celsius=average_temp, gas=gas)  # kg/m3
+    df[f"{gas}_kg_m3"] = gd * (df[f"{gas}_normalised"] * 1e-6)  # kg/m3
+    df[f"{gas}_kg_h_m2"] = df[f"{gas}_kg_m3"] * df[wind] * 60 * 60  # kg/h/m2
+    return df