CORE PRINCIPLES
What to establish first
- Conservation of mass links flow rate, area and average velocity.
- Energy balance relates pressure, velocity and elevation head.
- Friction and fittings create irreversible head loss.
Fluid Mechanics
Flow, pressure loss, velocity, head and hydraulic behavior.
Steady-state, single-phase incompressible liquid series piping and rotodynamic pump analysis. Branch networks, gas flow and transients are outside workspace scope.
MODULE OVERVIEW
Fluid Mechanics in practical engineering work.
Fluid mechanics describes how pressure, velocity, elevation and friction govern liquid and gas movement. A useful model begins by defining the fluid, operating condition, boundaries and whether compressibility matters.
DESIGN CONCEPTS
Terms worth checking
- Continuity
- Bernoulli head
- Reynolds number
Common applications: Pipe sizing · Cooling circuits · Process transfer lines
KEY RELATIONSHIP
Continuity for a filled circular pipe
v = Q/A
- Q — volumetric flow, m³/s
- A — internal flow area, m²
- v — average velocity, m/s
This gives a cross-section average; the velocity profile and pressure loss need further analysis.
WORKED EXAMPLE
Known values → substitution → interpretation
- Known values
- Q = 18 m³/h; D = 80 mm
- Method
- Convert Q to 0.005 m³/s and use A = πD²/4
- Interpretation
- The average velocity is about 0.995 m/s.
KEY DESIGN CHECKS
Confirm the conditions behind the number
- Define the governing load case, duty cycle and required design life before using a simplified relation.
- Use compatible units and material data for the actual condition, temperature and manufacturing state.
- Compare the result with strength, stiffness, fatigue, safety, serviceability and applicable-code requirements.
COMMON ENGINEERING MISTAKES
Keep the model within its scope
- Applying continuity for a filled circular pipe outside the assumptions shown on this page.
- Using a nominal condition while a peak, alternating, transient or environmental case governs the design.
- Treating a calculated value as a final component selection without checking interfaces, tolerances and the current governing standard.
AVAILABLE CALCULATORS
Select a calculator
RELATED RESOURCE
Open Pipe Flow Velocity Calculator
Convert flow and pipe diameter into a traceable average velocity.
Open related resource →REFERENCES & LIMITATIONS
Use this content as a transparent starting point
ReferenceR. W. Fox, A. T. McDonald and P. J. Pritchard, Introduction to Fluid Mechanics.ScopeRelationships are presented for the assumptions stated on this page and linked tool.Design reviewCheck material condition, loads, environment and the applicable current code.SafetyResults are educational/preliminary and do not certify safety or compliance.
RELATED ENGINEERING