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Knowledge card

Continuity Equation

Mathematical Modelling — Fluid Dynamics & Heat TransferContinuum mechanics; boundary-layer similarity theory

T⁻¹

Symbol

Conservation of mass for an incompressible flow.

Main equation
Dimension:T⁻¹ (s⁻¹)Maths:𝔹 equation(·, ·, ·) — A statement that two sides are equal, depending on another quantity, another quantity, another quantityDimensionally verifiedMathematically verifiedFully reduced to base quantities

In words:plusequalszero.

Open full derivation chain: 1 stepsDerivation
  1. Open Step 1: Given / definition
    Given / definition
    Level 0 · more available
    Brief — named quantities
    About levels

    Why the levels load one at a time

    Only level 0 travels with this article. The complete expansion is several megabytes, so deeper levels are fetched one at a time when you ask for them — and how deep it goes is not known until you get there.

    To go deeper still, open any quantity in the reading as its own concept card — it carries its own derivation and its own depth ladder.

    How many levels remain is not yet known — the depth is discovered one level at a time.

Equation Workspace

Set known values, calculate unknowns, inspect dependencies, and run numerical solves.

Calculator

Equation workspace

Set the values you know, then calculate the remaining quantities in Continuity Equation.

Domain Analysis

Unit status, dimensional trails, per-step checks, and custom unit expressions.

Step-by-step unit check (1 steps)
  1. Step 1 given
    Expand checked this step.
Try your own — the unit calculator

Ever wondered whether a formula “adds up”? This tool answers one plain question: do the units match? Pick a couple of quantities (distance, time, a speed…), join them with ×, ÷, +, or =, and press Run. It works out the resulting unit — for example distance ÷ time gives a speed, LT⁻¹ (metres per second) — and flags anything that can’t be right, like adding a length to a time.

Reads as: ∇·u

“∇·u” is analysed by expanding its full defining equation (its children and their relations), not as a bare symbol. Use Check this concept’s units above for the same result.

Mathematical Analysis

Object type, lawful operations, conditions, comparisons, and derivation-step checks.

Check one step at a time (1 steps)
Step 1 — given
Equation

Dimension I

Definition

What it is — and what it is not

What it is
  • S1Conservation of mass for an incompressible flow.
    • S1.1essenceThe sum of ∂u/∂x and ∂v/∂y. [1.1]
    • S1.2essence(∂u/∂x + ∂v/∂y) set equal to 0. [1.1]
Wisdoms
  • S2It forces the velocity field to be divergence-free.

Dimension II

In practice

How to deal with it

No practical guidance recorded yet.

Sub-topics 3

Related

References

  1. Majumdar (2021), continuum incompressible mass conservation; not an Aziz article equation locator.

    • 1.1

      Incompressible continuity — The universal two-dimensional incompressible balance u_x+v_y=0; the seeded stream function satisfies it identically.

      Corroborated
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