### 5.9.3. Drift and Slip Relations

You now define the slip velocity to be the phasic velocity relative to the continuous phase:

| (5–181)

and the drift velocity as:

| (5–182)

The slip and drift velocities are related by:

| (5–183)

With these relationships, the phasic continuity equation may be written in terms of mass fraction and drift velocity as:

| (5–184)

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