Normal Shock Relationships
Fluid Mechanics · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- A normal shock wave is a physical mechanism that slows a flow from supersonic to subsonic. It occurs over an infinitesimal
- distance. The flow upstream of a normal shock wave is always supersonic and the flow downstream is always subsonic as
- The following equations relate downstream flow conditions to upstream flow conditions for a normal shock wave.
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
normal shock relationships in a supersonic wind tunnel diffuser Given upstream Mach number (M_1) = 2.4000; specific heat ratio (k) = 1.3600, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 2.4000, specific heat ratio (k) = 1.3600.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.5159 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.0317 — kept a factor of two that cancels in the correct rearrangement.
- 0.2579 — dropped that same factor in the other direction.
- 0.5675 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships ahead of a blunt body in supersonic flow Given upstream Mach number (M_1) = 1.2500; specific heat ratio (k) = 1.3800, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 1.2500, specific heat ratio (k) = 1.3800.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.8121 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.6243 — kept a factor of two that cancels in the correct rearrangement.
- 0.4061 — dropped that same factor in the other direction.
- 0.8934 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships for flow in a supersonic nozzle Given upstream Mach number (M_1) = 1.2000; specific heat ratio (k) = 1.3500, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 1.2000, specific heat ratio (k) = 1.3500.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.8413 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.6826 — kept a factor of two that cancels in the correct rearrangement.
- 0.4206 — dropped that same factor in the other direction.
- 0.9254 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships in a supersonic wind tunnel diffuser Given upstream Mach number (M_1) = 2.4500; specific heat ratio (k) = 1.3900, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 2.4500, specific heat ratio (k) = 1.3900.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.5161 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.0322 — kept a factor of two that cancels in the correct rearrangement.
- 0.2581 — dropped that same factor in the other direction.
- 0.5677 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships ahead of a blunt body in supersonic flow Given upstream Mach number (M_1) = 1.7500; specific heat ratio (k) = 1.3500, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 1.7500, specific heat ratio (k) = 1.3500.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.6228 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.2457 — kept a factor of two that cancels in the correct rearrangement.
- 0.3114 — dropped that same factor in the other direction.
- 0.6851 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships for flow in a supersonic nozzle Given upstream Mach number (M_1) = 1.3000; specific heat ratio (k) = 1.3600, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 1.3000, specific heat ratio (k) = 1.3600.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.7846 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.5693 — kept a factor of two that cancels in the correct rearrangement.
- 0.3923 — dropped that same factor in the other direction.
- 0.8631 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships in a supersonic wind tunnel diffuser Given upstream Mach number (M_1) = 2.5500; specific heat ratio (k) = 1.3900, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 2.5500, specific heat ratio (k) = 1.3900.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.5064 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.0128 — kept a factor of two that cancels in the correct rearrangement.
- 0.2532 — dropped that same factor in the other direction.
- 0.5571 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships ahead of a blunt body in supersonic flow Given upstream Mach number (M_1) = 1.4000; specific heat ratio (k) = 1.3900, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 1.4000, specific heat ratio (k) = 1.3900.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.7392 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.4785 — kept a factor of two that cancels in the correct rearrangement.
- 0.3696 — dropped that same factor in the other direction.
- 0.8131 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships for flow in a supersonic nozzle Given upstream Mach number (M_1) = 2.9500; specific heat ratio (k) = 1.3400, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 2.9500, specific heat ratio (k) = 1.3400.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.4645 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.9290 — kept a factor of two that cancels in the correct rearrangement.
- 0.2323 — dropped that same factor in the other direction.
- 0.5110 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships
normal shock relationships in a supersonic wind tunnel diffuser Given upstream Mach number (M_1) = 2.1500; specific heat ratio (k) = 1.3700, determine the downstream Mach number (M_2).
Given
Find
downstream Mach number (M_2)
Start with the thinking
- The governing relation printed in this handbook section is Normal shock relationships.
- Everything except M_2 is given, so isolate M_2 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Normal shock relationships give the downstream Mach number for supersonic flow crossing a normal shock.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that M_2 stands alone on the left-hand side.
Step 3 — List the givens: upstream Mach number (M_1) = 2.1500, specific heat ratio (k) = 1.3700.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning M_2 = 0.5493 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.0987 — kept a factor of two that cancels in the correct rearrangement.
- 0.2747 — dropped that same factor in the other direction.
- 0.6043 — rounded an intermediate value before the final step.
Reference: FE Handbook — Normal Shock Relationships