# Harold Mirels
Harold Mirels (1924–2023) was an aerospace researcher whose career at NACA and [The Aerospace Corporation](https://www.edgepedia.org/the-aerospace-corporation) included work on shock-tube boundary layers and cw chemical lasers; he was elected to the National Academy of Engineering's Aerospace section in 1986.[1](https://snaccooperative.org/view/13684868)
| Key fact | Detail |
|---|---|
| Life dates | Born 1924, died 2023[1](https://snaccooperative.org/view/13684868) |
| NACA technical note | Boundary layers behind shocks, May 1956, NACA Lewis Flight Propulsion Laboratory[2](https://digital.library.unt.edu/ark:/67531/metadc56000/) |
| Correlation accuracy | Laminar shock-tube formulas match numerical solutions to within fractions of a percent[3](https://doi.org/10.1063/1.1761839) |
| Correlation coverage | Air to shock Mach number 22; argon to 10[3](https://doi.org/10.1063/1.1761839) |
| Laser result | cw HF ring-laser forward-wave brightness halves at a 200-microrad reverse-wave suppressor mirror tilt[4](https://doi.org/10.1364/ao.25.000666) |
| Archival source | Oral history interview, 31 January 1985, AIP Niels Bohr Library[1](https://snaccooperative.org/view/13684868) |
## Early career: NACA and gasdynamics
Mirels worked at NACA's Lewis Flight Propulsion Laboratory, where he authored the May 1956 technical note *Boundary Layer Behind Shock or Thin Expansion Wave Moving Into Stationary Fluid*.[2](https://digital.library.unt.edu/ark:/67531/metadc56000/) The note determined the boundary layer behind a shock or thin expansion wave advancing into stationary fluid, and found that the thin-expansion-wave assumption was valid only for weak expansions, becoming progressively less accurate for strong ones.[2](https://digital.library.unt.edu/ark:/67531/metadc56000/) Its turbulent-boundary-layer solutions extended empirical semi-infinite flat-plate data to the case of a moving wall, the foundation of the later Mirels shock-tube test-time correlation.[2](https://digital.library.unt.edu/ark:/67531/metadc56000/)
## Career at The Aerospace Corporation
By the mid-1960s Mirels was at The Aerospace Corporation; his November 1965 blast-simulation paper credits him there.[5](https://doi.org/10.2514/3.3321) His output in this period was applied gasdynamics. In 1964 he co-authored with Richard R. Gold and James F. Mullen an AIAA Journal paper on a minimum-length magnetohydrodynamic (MHD) accelerator with constant enthalpy and magnetic field (2(6):1141–1143), and separately published an analytical solution for a constant-enthalpy MHD accelerator (2(1):145–146).[6](https://doi.org/10.2514/3.3099) In November 1965 he and Mullen published *Aerodynamic Blast Simulation in Hypersonic Tunnels* in AIAA Journal, addressing how blasts could be reproduced in hypersonic ground facilities.[5](https://doi.org/10.2514/3.3321) A 1968 AIAA Journal paper treated subsonic flow of hot gas through a highly cooled channel.[7](https://doi.org/10.2514/3.4816) One publisher record snippet suggests he joined The Aerospace Corporation in 1967, but the 1965 blast-simulation paper already credits him there, so the 1967 date is not used here.[7](https://doi.org/10.2514/3.4816) • [5](https://doi.org/10.2514/3.3321)
## Shock-tube boundary layers and the Mirels correlation
Mirels's 1964 AIAA Journal paper, *Shock Tube Test Time Limitation Due to Turbulent Wall Boundary Layer* (2(1):84–93), set out the turbulent test-time limitation that bears his name.[8](https://doi.org/10.2514/3.8736) His laminar correlation formulas agree with his numerical solutions to within fractions of a percent, with charts and tables covering air at shock Mach numbers up to 22 and argon up to 10.[3](https://doi.org/10.1063/1.1761839)
In 1983 he presented revised estimates of the turbulent boundary layer behind a uniformly moving shock at the AIAA 21st Aerospace Sciences Meeting as corresponding author at The Aerospace Corporation,[9](https://doi.org/10.2514/6.1983-567) and in 1984 an AIAA Journal paper tabulated numerical results for turbulent boundary-layer properties in air beginning at shock [Mach number](https://www.edgepedia.org/mach-number) 1.01 and extended the theory to wall blowing effects.[8](https://doi.org/10.2514/3.8736)
## Key publications
**Turbulent boundary layer behind constant velocity shock including wall blowing effects (AIAA Journal, 1984).** The paper applied Mirels's earlier theory to obtain numerical results for turbulent boundary-layer properties in air, tabulated for shock Mach numbers from 1.01 upward, and added wall blowing effects.[8](https://doi.org/10.2514/3.8736)
**Reverse-wave suppressor mirror effects on cw HF unstable ring laser performance (Applied Optics, 1986).** In a continuous-wave hydrogen fluoride unstable ring laser, Mirels measured and analyzed the effect of the reverse-wave suppressor (RWS) mirror that damps the counter-propagating wave. Forward-wave far-field brightness proved very sensitive to RWS mirror tilt, falling by a factor of 2 at a 200-microrad tilt; an aberrated RWS mirror cut this tilt sensitivity by nearly an order of magnitude. He also proposed a mechanism by which conventional-mirror tilt reinforced a higher-order mode in the forward output, which the aberrated mirror did not. The paper shows about 2 citations per iCite, consistent with a niche but program-relevant resonator study.[4](https://doi.org/10.1364/ao.25.000666)
**Correlation formulas for laminar shock tube boundary layer (Physics of Fluids).** This paper supplied the closed-form formulas matching numerical solutions to within fractions of a percent, with charts and tables for air (Mₛ ≤ 22) and argon (Mₛ ≤ 10).[3](https://doi.org/10.1063/1.1761839)
## By the numbers
Citation counts for Mirels vary by database and cannot be settled from the available records: one AIAA-linked record gives h-index 16 with 915 citations, another gives h-index 18 with 1,473 citations, and rankless.org gives h-index 15 with 720 indexed citations (914 total).[8](https://doi.org/10.2514/3.8736) • [10](https://www.rankless.org/authors/h-mirels) These are reported as an unresolved discrepancy rather than reconciled. The 1986 laser paper's headline number, a factor-of-2 brightness loss at 200 microrad of mirror tilt, quantifies how tightly cw chemical laser resonators had to be aligned.[4](https://doi.org/10.1364/ao.25.000666)
## References
1. [Mirels, Harold, 1924– — Social Networks and Archival Context](https://snaccooperative.org/view/13684868)
2. [Boundary Layer Behind Shock or Thin Expansion Wave Moving Into Stationary Fluid, NACA TN, May 1956](https://digital.library.unt.edu/ark:/67531/metadc56000/)
3. [Correlation Formulas for Laminar Shock Tube Boundary Layer, Physics of Fluids](https://doi.org/10.1063/1.1761839)
4. [Reverse-wave suppressor mirror effects on cw HF unstable ring laser performance, Applied Optics, 1986](https://doi.org/10.1364/ao.25.000666)
5. [Aerodynamic blast simulation in hypersonic tunnels, AIAA Journal, 1965](https://doi.org/10.2514/3.3321)
6. [Minimum-length MHD accelerator with constant enthalpy and magnetic field, AIAA Journal, 1964](https://doi.org/10.2514/3.3099)
7. [Subsonic flow of hot gas through a highly cooled channel, AIAA Journal, 1968](https://doi.org/10.2514/3.4816)
8. [Turbulent boundary layer behind constant velocity shock including wall blowing effects, AIAA Journal, 1984](https://doi.org/10.2514/3.8736)
9. [Estimates of turbulent boundary layer behind a shock wave moving with uniform velocity in air, 21st Aerospace Sciences Meeting, 1983](https://doi.org/10.2514/6.1983-567)
10. [H. Mirels, rankless.org author profile](https://www.rankless.org/authors/h-mirels)
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*Topic: Encyclopedia › Technology and the built world › Engineers and computer scientists › Engineers and materials scientists › Researchers in mechanical and aerospace engineering, robotics, and control › Combustion and reacting flows*
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