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SD2155 Flow Acoustics 6.0 credits

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Headings with content from the Course syllabus SD2155 (Spring 2022–) are denoted with an asterisk ( )

Content and learning outcomes

Course contents

Mathematical tools. The fundamental equations of fluid mechanics. The classical wave equation and its solutions. The inhomogeneous wave equation. Lighthills theory for aerodynamic sound. Curles equation. The convective wave equation. Sound propagation in ducts and pipes. Multi-port theory. Sound from moving sources. (”Ffowcs Williams&Hawkings equation”). Fluid driven self sustained oscillators – Whistles. Applications with focus on fluid machines and vehicles.

Laboratory exercise: Measurement of 2-port for a muffler.

Project assignment: Analysis of an exhaust muffler.

Intended learning outcomes

To present the fundamental theories for sound generation and propagation in fluids with non-stationary (turbulent) flow fields.

Students graduating from the course should:

  • Be able to derive the classical wave equation and be familiar with the solutions under plane and spherical symmetry including Greens functions.
  • Be able to explain and apply a multipole-expansion and know the character of the simplest point sources (monopole, dipole, quadrupole).
  • Know about Lighthills acoustic analogy and its limitations and be able to explain the physical mechanisms that generate sound in a flow.
  • Know how flow and motion affects sound propagation and generation and be able to explain phenomena such as the Doppler-shift and the Mach-cone.
  • Be able to apply Lighthills analogy to fluid machines and vehicles and know how the different mechanisms scale with the flow speed.
  • Be able to explain how fluid driven self-sustained oscillators (”whistles”) are created and how they can be eliminated.
  • Be able to apply 2-port theory to analyse sound propagation in pipe and duct systems in particular with application to vehicle exhaust systems.
  • Have obtained training in experimental techniques for analysis of sound in ducts.

Course disposition

No information inserted

Literature and preparations

Specific prerequisites

Basic courses in mathematics, mechanics.

English B / English 6

Recommended prerequisites

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Examination and completion

If the course is discontinued, students may request to be examined during the following two academic years.

Grading scale

A, B, C, D, E, FX, F


  • LAB1 - Exercises, 1.0 credits, grading scale: P, F
  • LAB2 - Project, 1.0 credits, grading scale: P, F
  • TEN1 - Examination, 2.0 credits, grading scale: A, B, C, D, E, FX, F
  • ÖVN1 - Assignments, 2.0 credits, grading scale: P, F

Based on recommendation from KTH’s coordinator for disabilities, the examiner will decide how to adapt an examination for students with documented disability.

The examiner may apply another examination format when re-examining individual students.

Other requirements for final grade

Written examination (TEN1; 2 university credits), approved exercises (ÖVN1; 2 university credits) approved measurement exercises (LAB1; 1 cr) and project work (LAB2; 1 university credits).

Opportunity to complete the requirements via supplementary examination

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Opportunity to raise an approved grade via renewed examination

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Ethical approach

  • All members of a group are responsible for the group's work.
  • In any assessment, every student shall honestly disclose any help received and sources used.
  • In an oral assessment, every student shall be able to present and answer questions about the entire assignment and solution.

Further information

Course web

Further information about the course can be found on the Course web at the link below. Information on the Course web will later be moved to this site.

Course web SD2155

Offered by

Main field of study

Mechanical Engineering

Education cycle

Second cycle

Add-on studies

SD2165 Acoustical Measurements
SD2150 Experimental Structure Dynamics
SD2175 Numerical Methods for Acoustics and Vibration
SD2180 Non-Linear Acoustics
SD2190 Vehicle Acoustics and Vibration
SG2218 Turbulence


Susann Boij (