�?�?t ε l ρ l v l + �?�?ε l ρ l v l v l = ε l �?�?τ l + ε l ρ l g �?ε l �?p �?β v l �?v s If the amount of fluid inside the wellbore drops due to lost circulation (or https://directoryarmy.com/listings13649217/about-drilling-fluid-loss