Lorenz Sigurdson


BASc Engineering Science, Aerospace (Toronto)
MSc (Caltech)
PhD (Caltech)

Position Summary/ Research Interest:


education, engineering creativity, fluid mechanics, aerodynamics, aerospace, vortex fluid dynamics, flow visualization, flow control, separated flows, large-scale structures, turbulence, impacting drops, vortices, DNA micro-arrays, digital materials printing, inkjets


EDUCATION: Seeking methods to inspire undergraduates' creative thinking in their capstone design course designs, and graduate students in their creation of new scientific knowledge and experimentation.

RESEARCH: One of my interests is the structure and control of turbulent and droplet flows. Within the apparent chaos of turbulence, orderly large-scale vortex structures often exist. Knowledge of these is significant to modeling and understanding. It offers the potential to control turbulent flows to the Engineer’s advantage using unsteady and possibly spatially varying forcing techniques such as sound, moving control surfaces, and micro-electro-mechanical devices (MEMs). This can result in drag reduction on automobiles and aircraft, reduced pressure losses in piping systems, and improved efficiency for a variety of mechanical devices and industrial processes.

A long-term goal is consideration of all the flows for fundamental understanding of vortex dynamics, turbulence and ultimately flow control. The scientific approach uses flow visualization experiments to reveal the large-scale structures, and image processing techniques to study them. With the new knowledge of the structures, attempts can be made to manipulate them in advantageous ways. Anticipated results are the development of techniques and devices to control the turbulence leading to marketable technology.


With the help of many dedicated individuals, I have created the Vortex Fluid Dynamics Laboratory (VFDL) at the U of A. Currently we are controlling the turbulent flow over a backstep with a device we call the "RoboStep" in the High Speed Water Tunnel facility. This uses a sophisticated actuator system to create a spanwise-varying forcing to influence the 3-D vortex structures in the turbulent separated flow downstream of the step, thereby increasing the mixing and reducing the drag. This has involved development of a new diagnostic technique using tufts that operate in water and image processing to measure the length of the separated region. We are also using our state-of-the-art digital materials printer that produces pico-liter droplets to investigate the challenges of producing DNA micro-arrays ("gene chips" or "biochips"), other labs-on-chips, and potentially, fuel cell catalyst deposition.

Here are some examples of other flows and diagnostics we have worked on at the VFDL:

  1. An impacting water drop on the free surface of the water in a tank as a function of fall height. Significant contributions have been made to the theory of vorticity creation at air-water interfaces, and the mechanisms controlling vortex ring penetration depth. Impacting drops are important to many Engineering solutions. We collaborate with colleagues at the National University of Singapore, E.T.H. in Zurich, Switzerland and D.T.U. in Denmark. With the latter two we have developed a supercomputer simulation of the three-dimensional unsteady vortex structure created by an impacting water drop.
  2. The 3-D vorticity generated by a bursting air bubble resting on a pool of water (the inverse of the first flow). Our lab has produced the first detailed photographs of this phenomenon. The mechanism of vorticity evolution is a focus.
  3. The flow through a flat plate orifice meter and its response to unsteady excitation. The flow through the meter was visualized to determine the mechanism of the effect of pulsation on the calibration coefficient. A very significant metering error can result which is important to revenue calculation. This was done in collaboration with Nova Natural Gas Transmission Ltd (now TransCanada Pipelines).
  4. Flow control of a smoke stack in a cross wind that is experiencing a downwash of the emissions. Attempts are being made to alleviate the problem through the use of acoustic excitation and a synthetic jet actuator. Elimination of downwash that brings toxic stack emissions dangerously close to the ground is healthier for people and less capital intensive for stack construction or refitting. This is a jet in a cross flow that occurs in gaswell flaring and combustion chambers.
  5. We have developed an Image Correlation Velocimetry technique which calculates the velocity field from successive images of a scalar tracer. It has been used on the wake of a cylinder, where we have discovered a new “void” vortex structure. We have also been developing a 3-D Visualization System that uses two digital Nikon cameras to capture stereoscopic images of turbulent flow structures, and a 3-D Digitization System to extract data from the images.
  6. A collaboration with Big Iron Drilling Ltd. of Edmonton concerned the optimization of the jet pump in their “Iron Eater” water softener. A superior product resulted from streamlining the inlet portion, using flow visualization to locate separations, and experimenting with different jet configurations. The transport of catalyst particles is an important part of this project.


Sample Refereed Journals (many more to add):

  1. Gilbert, S. and Sigurdson, L., 2005, “Hydrogen Bubble Flow Visualization of a Self-oscillating Cylinder Vortex Street ‘Void’”, Physics of Fluids 17,1, Sept. ,2005, 1 page.
  2. Sigurdson, L.W., Apps, C.P., and Chen, T., 2003, “Two Color Image Correlation Velocimetry Applied to Turbulent Smoke-Wire Streaklines,” Experiments in Fluids 35, Sept, 2003, pp 288-290.
  3. Bucholz, J. and Sigurdson, L., 2002, “An Apparatus to Study the Vortex Ring Structure Generated by a Bursting Bubble”, Measurement Science and Technology, Vol.13, pp 428-437.
  4. Diep, J. and Sigurdson, L. 2001, “Cross-Jet Influenced by a Concentric Synthetic Jet”, Physics of Fluids, Vol. 13, No. 9, Sept., page S16.
  5. Buchholz, J. and Sigurdson, L.W., 2000, “The Kinematics of the Vortex Ring Structure Generated by a Bursting Bubble”, Physics of Fluids, Vol. 12, No. 1, Jan, pp 42-53.
  6. Peck, B. and Sigurdson, L.W., 1999, “Geometry Effects on Free Surface Vorticity Flux ”, ASME Journal of Fluids Engineering, ASME Journal of Fluids Engineering, Vol. 121, Sept. 1999, pp. 678-683.
  7. Peck, B. and Sigurdson, L., 1998, “On the kinematics at a free-surface”, IMA Journal of Applied Mathematics, Vol. 60, pp. 1-13.
  8. Sigurdson, L.W., 1997, “Flow Visualization in Turbulent Large-Scale Structure Research”, Flow Vis. Soc. Japan, Atlas of Visualization, Vol. III, pp. 99-113.
  9. Sigurdson, L.W. and Chapple, D., 1997, “Visualization of Acoustically Pulsated Flow Through an Orifice Plate Flow Meter”, accepted for publication July, 1997, Journal of Flow Visualization and Image Processing.
  10. Sigurdson, L.W., 1995, “The Structure and Control of a Turbulent Reattaching Flow”, Journal of Fluid Mechanics 298, pp. 139-165.
  11. Peck, B., Sigurdson, L.W., Faulkner, B. and Buttar, I., 1995, “An Apparatus to Study Drop-Formed Vortex Rings”, Measurement Science and Technology, Vol. 6, pp. 1538-1545.
  12. Peck, B. and Sigurdson, L.W., 1995, “The Vortex Ring Velocity Resulting from an Impacting Water Drop”, Experiments in Fluids 18, pp. 351-357.
  13. Peck, B. and Sigurdson, L.W., 1994, “The Three-Dimensional Vortex Structure of an Impacting Water Drop”, Physics of Fluids, Vol. 6, No. 2, Pt. 1, pp. 564-576.
  14. Buchholz, J., Sigurdson, L. and Peck, B., 1995, “Bursting Soap Bubble”, Physics of Fluids, 7, 9, p.S3.
  15. Peck, B. and Sigurdson, L., 1992, “Impacting Water Drops”, Physics of Fluids A, 4, 9, p. 1872.
  16. Sigurdson, L.W., 1991, “Atom-Bomb/Water Drop”, Physics of Fluids A, Vol. 3, No. 9, p. 2034.
  17. Peck, B. and Sigurdson, L., 1991, “Impacting Water Drop”, Physics of Fluids A, 34, 9, p. 2032.

Contributions to Textbooks:

  1. Sigurdson, L.W., 2005, “Application Spotlight – What Nuclear Blasts and Rain Drops Have in Common”, Introductory Fluid Mechanics, by Cengel, Y. and Cimbala, J., McGraw-Hill, 1 page.
  2. Sigurdson, L., 2005, “Application Spotlight – How Orifice Plate Flow Meters Work, or Do Not Work”, Introductory Fluid Mechanics, by Cengel, Y. and Cimbala, J., McGraw-Hill, 1 page.
  3. Tsinober, A., 2001, “Atom-Bomb/Water Drop”, my photographic comparison was used and discussed in An Informal Introduction to Turbulence, Series: Fluid Mechanics and Its Applications, Vol. 63, Kluwer Academic Publishers. From the Kluwer website: “This book will certainly be of interest and use to graduate students as well as scientists active in fields where the turbulence of fluids is of importance.”

Other Book Contributions:

  1. Buchholz, J., Sigurdson, L.W., and Peck, B., 2004, “Bursting Soap Bubble”, Gallery of Fluid Motion, Samimy, M.; Breuer, K. S.; Leal, L. G.; Steen, P. H.,Jan. 1,2004, Cambridge University Press, 1 page.
  2. Peck, B. and Sigurdson, L.,2004, “Impacting Water Drops”, Gallery of Fluid Motion, Samimy, M.; Breuer, K. S.; Leal, L. G.; Steen, P. H.,Jan. 1,2004, Cambridge University Press, 1 page.
  3. Sigurdson, L.W., 2004,“Atom-Bomb/Water Drop”, Gallery of Fluid Motion, Samimy, M.; Breuer, K. S.; Leal, L. G.; Steen, P. H.,Jan. 1,2004, Cambridge University Press, 1 page.
  4. Guyon, Etienne, Hulin, Jean-Pierre and Petit, Luc, 2005,"Ce Que Disent les Fluides" (What Fluids Say), published by "Belin - pour la Science" (the publisher of the French Version of Scientific American), expected in September, 2005, I contributed comparison images of the Atom Bomb/Water Drop to be part of a two page section on large-scale structures in turbulence.
  5. Buchholz, J., Sigurdson, L. and Peck, B., 1999, “Bursting Soap Bubble”, “Flow Visualization: Techniques and Examples”, Smits, L. and Lim, T.T. eds., Imperial College Press, 1 page, 1999.

Other Refereed Publications:

  1. Sigurdson, L., 2003, “Flow Visualization in Large-Scale Structure and Flow Control Research”, 7th Asian Symposium on Visualization, Nov 3-6, 2003, Singapore, 9 pages, invited keynote presentation.
  2. Diep, J. and Sigurdson, L., 2003, “Low Velocity Ratio Transverse Jets Influenced by Concentric Synthetic Jets”, “Manipulation and Control of Jets in Crossflow” a Springer-Verlag text edited by A. Karagozian and L. Cortelezzi, based on our presentation at the CISM (International Centre for Mechanical Sciences) Workshop on Analysis and Control of Transverse Jets for Industrial and Environmental Application, Udine, Italy, June 14-15, 2001, pp 257-269.
  3. Sigurdson, L. and Apps, C., 2003, “Image Correlation Velocimetry Applied to Diffuse Smoke in a Turbulent Jet”, Proc. Canadian Congress of Applied Mechanics (CANCAM), Vol. I, eds. Epstein, M. Sudak, L. and Budiman, A., Univ. of Calgary, Calgary, AB June 1-5, pp 76-77.
  4. Sigurdson, L. and Diep, J., 2002 “Mixing in a Cross-Jet Enhanced by a Coaxial Annular Synthetic Jet”, invited paper* accepted for publication in an IUTAM hardcover book Turbulent Mixing and Combustion, August 2001 (8 book pages). *based on a presentation at the invitation-only IUTAM 2001 symposium by the same name.
  5. Sigurdson, L. and Diep, J., 2001, “Mixing in a Cross-Jet Enhanced by a Coaxial Annular Synthetic Jet”, Book of abstract for invitation on IUTAM Symposium on Turbulent Mixing and Combustion, Queen’s University, Kingston, Ontario, Jue 3-6, pp. 24-26.
  6. Sigurdson, L.W. and Chapple, D., 1998, “A Turbulent Mechanism for Pulsation-Induced Orifice Plate Flow Meter Error”, presented at the 13th Australasian Fluid Mechanics Conference, 13-18 Dec. 1998 at Monash University, Melbourne, Australia, Proceedings, Thompson, M.C. and Hourigan, K. eds, Vol. 1, pp. 67-70.
  7. Peck, B. and Sigurdson, L., 1998, “Vortex Dynamics at Fluid Interfaces”, presented at the 13th Can. Symp. on Fluid Dynamics and 19th Am. Mtg. of Can. Appl. Math. Soc., Vancouver, B.C., May 28-31, 1998, Book of Abstracts, p. 132.
  8. Sigurdson, L.W. and Chapple, D., 1997, “Visualization of Acoustically Pulsated Flow Through an Orifice Plate Flow Meter”, Proc. of the 1st Pacific Image Processing and Flow Visualization Conf., Honolulu, Hawaii, Feb. 23-26, 1997.
  9. Sigurdson, L.W., 1996, “The Vortex Dynamics of a Turbulent Reatta

Lorenz Sigurdson

Professor Emeritus

Office: 10-369 Donadeo Innovation Centre for Engineering