Site: Lavrentyev Institute of Hydrodynamics
15 Lavrentyev Prospect
Novosibirsk, 630090, Russia
Phone: (3832) 357158
Fax: (3932) 354050
Telex: 133149 PTB SU
Email: root@hydro.nsk.su

Date Visited: October 31, 1995 WTEC Attendees:

L. Gentry & H. B. Ali (report authors), R. Blidberg, S. Chechin, M. J. DeHaemer, J. Moniz, J. B. Mooney, D. Walsh

Hosts:

Acad. Vladimir M. Titov

Director of Institute

Prof. Igor V. Yakovlev

Vice Director

Prof. Valery K. Kedrinskii

Vice Director

Prof. Vladislav V. Mitrofanov

Head, Detonation Processes Lab.

Prof. Victor I. Bukreev

Head, Experimental Applied Hydrodynamics Lab.

Prof. Izolda V. Sturova

Head, Wave Hydrodynamics Lab.

BACKGROUND

The Lavrentyev Institute of Hydrodynamics (LIH) was the first institute founded at the Akademgorodok (Academic City). The LIH was founded in 1957 by Academician M. A. Lavrentyev with three immediate goals for the Akademgorodok: development of the main research directions, establishment of active relations between science and industry, and training of young research fellows for advanced science and engineering.

Research Fellows of the LIH head four chairs at the Novosibirsk State University: Hydrodynamics; Theoretical Mechanics; Continuum Physics; and Solid Mechanics. Approximately 500 people are employed at LIH, including 170 scientific personnel. The scientific staff includes 130 to 140 Ph.D.s, 43 doctors, three academicians, and two corresponding members of the Russian Academy of Sciences. LIH is the founder and publisher of three scientific journals with international distribution: Combustion and Explosion Physics, Applied Mechanics and Technical Physics, and Continuum Mechanics.

The institute does fundamental and applied science in the areas of mathematical problems of continuum mechanics, applied hydrodynamics, solid mechanics, and detonation and explosion processes.

Director Titov gave an overview of the institute and introduced heads of various laboratories where he felt we might have an interest. During his opening remarks he made the following points.

RESEARCH AND DEVELOPMENT ACTIVITIES

Two of the institute's areas of research were described in detail: detonation processes and applied hydrodynamics.

Laboratory for Dynamic Loading of Condensed Matter

Prof. Igor V. Yakovlev described the work of this laboratory. The institute has a widely varied effort in fundamental and applied research in explosive working of materials and high-velocity processes. These activities include numerical simulation and experimental study of detonation and shock wave flows and deformation and failure processes under impulse loads. The institute has a long history of experience in explosive working of materials including hardening, welding, compaction, forming of structures from powders, and detonation spraying. Some of these processes and the resulting products were described and shown to us. We also visited two laboratories. One was outfitted with a variety of explosive containment chambers for experiments in materials forming and welding and the other for detonation spraying.

Explosive welding processes, involving melting and fusing of metals, have been developed at the institute for over 30 years, and many techniques are now used commercially in Russia to form metallic and bi-metallic structures where high strength and low cost is desired. Also, special bi-metal welding processes have been developed for unique applications such as components for reduced galvanic corrosion in ship systems.

Hardening is different from welding in that explosive mechanical deformation is used to harden 1 to 2 mm thicknesses of the surface. Their work in hardening has been transferred to a Novosibirsk factory where large chambers capable of accommodating 2-3 kg of explosives are operated.

They also have developed an explosive liquid extrusion process for forming plate, which was not described to us in any detail.

Compaction is another process they have developed, especially in bonding of metals to non-metals such as copper to ceramics where special electrical conductive and isolation characteristics are required and in swaging of cables to fittings using primacord. Explosive compaction devices have been used extensively in the electrical cable industry in Russia.

Explosive forming of metal and ceramic matrices is also an area of research at the institute. Metallic or ceramic powders are compacted in a 2-3 microsecond impulse that does not change the properties of the powder. This process can also be used to form metal structures with embedded composite fibers or metal alloys consisting of small spheres. They have a contract with Dynamit Nobel relating to this last process.

Detonation Processes Laboratory

Prof. Vladislav V. Mitrofanov, Head of the Detonation Processes Laboratory, presented its work.

Detonation spraying is one of their important developments over the past decade. We were shown a laboratory demonstration of the technique which involves deposition of a thin film of powdered coating on a parent material by a microwelding process. The powder is thrown onto the target object by a mixed-gas automatic detonation gun (ADU "Ob") at velocities of 1500 m/sec and temperatures of about 4000°C. Detonation pulses of up to 6 shots per second apply coatings of up to 10 microns of thickness per shot. The powder is melted and firmly bonded to the surface on a molecular level. A variety of coatings and parent materials are used to achieve desired characteristics of precise thickness, hardness, wear-resistance, corrosion/erosion protection, etc. This process is a cost-effective technique for restoring worn parts to full reusability. Typically the gun is fixed, and the target position may be computer controlled to apply the coating where desired and in thicknesses required. The patented coating technique has resulted in more than 20 "Ob" units in use in various Russian enterprises and research institutes.

The fundamental research in explosive processes at LIH is considered of the first rank in Russia, and they have a number of industrial investigations going on with companies in Sweden, Japan, Germany, the United States, and Yugoslavia as well as in Russia. In their research they have used many different kinds of explosives to achieve a variety of loading rates, pressures, and temperatures for their processes in high velocity processes.

Department of Applied Hydrodynamics

The activities of the LIH in applied hydrodynamics cover the gamut from mathematical analyses of fundamental hydrodynamics to their application to very practical problems. The activities of the Laboratory of Stratified Flow and the Laboratory of Experimental Applied Hydrodynamics include: stratified and turbulent flows, wake characteristics, surface and internal wave generation mechanisms, the effects of waves on submerged bodies, and experimental testing of mathematical models and numerical computations in hydrodynamics.

Laboratory for Wave Hydrodynamics

Prof. Izolda V. Sturova presented some of their work on the motion of submerged objects in a stratified flow, particularly regarding the role of internal waves. The practical importance of this subject arises from the extensive development of underwater vehicles, submersibles, and offshore structures. When a body moves in a stratified fluid, it experiences hydrodynamic loads which are affected by the density variation. The dynamic interaction between the floating body and the stratified fluid includes a transfer of power from the body into the generation of internal waves. This leads to the well-known phenomenon of "dead water," studied by Nansen and Ekman at the end of the 19th century.

The group at LIH led by Prof. Sturova has conducted experimental and theoretical investigations of this problem and developed methods for calculating and studying surface and internal waves generated in different stable fluid stratifications. The experiments involved measurement of hydrodynamic loads due to internal waves on a restrained sphere located either below or within the pycnocline (the region of density change). The theoretical analysis, using the coupled finite element method, was based on the 2-D linear problem of radiation and scattering of small-amplitude surface and internal waves from a horizontal cylinder moving at a constant depth below the pycnocline. Previously, the problem of a submerged body advancing in regular water waves had been considered only for surface waves in a homogeneous fluid. The pycnocline variations were modeled by 2-and 3-layered fluids. In part, the experiments were designed to establish the limits of the theory, since the theories are linear, while the phenomena are non-linear.

Laboratory of Experimental Applied Hydrodynamics

Prof. Victor I. Bukreev, head of the Laboratory of Experimental Applied Hydrodynamics, provided an overview of the type of work being performed in his laboratory. He noted that the lab, which was organized 35 years ago, has solved 200 problems -- which he classified as either "fundamental problems" (initiated by his lab) or "applied problems" (originating externally). Most of the relevant experiments were conducted in laboratory conditions; however, six of them involved large-scale field investigations. The work has included joint projects with many groups in other cities of the former Soviet Union. Also, they have contracts with Russian companies and even with some American companies. As examples of the latter, Bukreev cited the development of a water-jet tank cleaner and a humidifier for American companies.

Much of the work of the group revolves around the areas of experimental investigations of wave motions, hydrodynamic stability and turbulence, and the motions of bodies in liquids. Bukreev mentioned several examples of the preceding, including the study of the effect of internal waves on a body. Unlike the work of Prof. Sturova, this was concerned with problems of the stability of the body, including an analysis of its pitch, heave, and roll. The forces acting on a stationary body (cylinder) were also investigated, since this body is used to study wave impact on fixed marine structures.

Bukreev provided some examples of innovative, in some cases even ingenious solutions to diverse problems. He was particularly enthusiastic in his description of the problem of the dynamics of a dropped sphere in unbounded fluids -- both homogeneous and two-layer fluids. In a perfectly symmetrical scenario, the sphere should descend in a straight line indefinitely. According to Bukreev, their experiments show that, in fact, the sphere does not descend in a straight line, but instead after a certain period of time, it suddenly swerves to one side. The same effect is observed in the case of a two-layer fluid (kerosene/water). Further, experiments revealed that a drop of kerosene may be trapped by the hydrodynamic wake behind the falling sphere to a distance of 30 to 40 sphere diameters, indicating stability of the "sphere-kerosene drop" composite. Bukreev claimed that these results are of fundamental significance but have received inadequate attention in the past. The basis for Bukreev's assertion is explained as follows:

The problem of the falling sphere was first noted by Newton and later observed by other scientists, particularly in the early decades of the 20th century. The results were summarized by L. Schiller in 1932. The major observation was the striking difference in drag coefficients of a free-falling sphere and a fixed sphere under otherwise similar conditions. In particular, under certain conditions, the drag coefficient of a free-falling sphere is three times larger than that of a fixed sphere. And yet, monographs on hydrodynamics contain only the classic curve of drag coefficient versus Reynolds number obtained by C. Wieselsberger for a fixed sphere. Results for the free-falling sphere have received inadequate attention, although some systematic experiments have been conducted (e.g., H. Viets and D. Lee 1971 and I. Nakamura 1976).

For a fixed sphere, the drag coefficient depends only on the Reynolds number, albeit in a complex manner. For a free-falling sphere, the solution depends on two parameters: a "kind of Reynolds number," and the density difference between the fluid and the sphere. In the general case, the desired dependence can be represented as a surface in 3-dimensional space or as a set of plane curves. Based on experimental data already published, only several dozen points on the set of curves can be found. Prof. Bukreev has obtained several points from his own experimental investigations.

Existing theory is inadequate, as it encompasses only a narrow range of parameters that have already been studied (the classic Stokes solution and its generalizations by early 20th century investigators). Further advances beyond this parameter range can be made only by experimental means. The existing sparse data fall into the parameter range of either definite stability or obvious instability. Little is known about the nebulous boundary between the two regions. Hence, there is a definite need for experimental data in this area.

Within a month of our site visit, a proposal was submitted to the Office of Naval Research by LIH for a two-year research effort to further investigate the problem of a falling sphere in homogeneous and two-layer fluids.

Underwater Explosions Laboratory

Prof. Valery K. Kedrinskii, deputy director of LIH, discussed some of the work being done in underwater explosions. The investigations encompass a broad spectrum of processes, including: shock wave generation and propagation, cavitation, fluid fracture under explosive loading, jet flows due to underwater explosions, and shock wave propagation in chemically active bubbly media.

As an illustration of the practical importance of the preceding research, Kedrinskii cited the phenomenon of accidental detonation in bubbly liquids, due to bubble cavitation. This was shown to be a possible explanation of large-scale fuel explosions in closed volumes under shock loading as a result of an accident during transportation. In particular, the energy absorbed by the cavitating bubbles from the incident shock wave is sufficient to raise their internal temperature to the ignition level, thereby causing the bubble explosion. Kedrinskii also discussed in some detail their efforts to develop various types of underwater acoustic charges. Over a period of about 20 years the institute has examined a variety of sound sources, including explosive cord line charges; a vertical line array of concentrated, single-frequency charges; ring charges; and spiral charges. The need for diverse source types derives from the different source characteristics (directivity, signal duration, and spectral content) required for various applications.

SUMMARY

The Lavrentyev Institute of Hydrodynamics is a prestigious scientific establishment and has done important fundamental research in mechanics, hydrodynamics, and detonation processes. They have seen some reduction in funding but have begun to successfully transition to international contracts to offset internal RAS funding losses. The area of explosion processes seems one of the most vibrant disciplines and also seems the most likely to provide processes and products for the civil sector.

The Laboratory of Applied Hydrodynamics has several decades of experience in diverse areas of hydrodynamics. Their contributions have ranged from development of innovative solutions to practical problems, to pioneering efforts in the fundamentals of hydrodynamics.

Some of the results in underwater explosions, cavitation, and submerged bodies have been published in English, but it would appear that they have been more productive than prolific.

REFERENCES

Lavrentyev Institute of Hydrodynamics. Brochure ca 1995. Overview and description of the institute and the main departments (In English).

Detonation Spraying, Equipment and Technology. ca. 1995. Booklet (in English) pictorially showing the capabilities of the detonation gun "Ob". 4 pages.

Ermanyuk, E., and I. Sturova. 1994. "Effects of regular waves on the body submerged in a stratified fluid." 20th Symposium on Naval Hydrodynamics, Santa Barbara, CA.

Bukreev, V. I. 1989. "Experimental investigation of the range of applicability of the solution of Stoke's second problem." Fluid Dynamics, vol. 23, No. 4, pp. 504-509, Plenum Publishing Corporation, New York.

Bukreev, V. I. 1989. "Instability of internal waves from a cylinder in a shear flow with a large Richardson number," op. cit., pp. 679-682.

Bukreev, V. I., and N. V. Gavrilov. 1984. "An experimental study of internal solitary waves in a two-layer liquid." Fluid Dynamics, pp. 652-657, Plenum Publishing Corporation, New York.

Bukreev, V. I., A. V. Gusev, and E. M. Romanov. 1993. "Effect of molecular diffusion on stratified shear flow stability." Fluid Dynamics, vol. 28, No. 1, pp. 25-29, Plenum Press Publishing Corporation, New York.

Bukreev, V. I., A. V., Gusev, and E. V. Ermanyuk. 1995. "Experimental study of the motion of a submerged body under the influence of internal waves." Fluid Dynamics, vol. 30, No. 2, pp. 326-330, Plenum Publishing Corp.

Kedrinskii, V. K. 1981. "Structural characteristics of shock waves from underwater explosions of helical charges." Journal of Applied Mechanics and Technical Physics, vol. 21, No. 5, pp. 617-623, Plenum Publishing Corporation.

Kedrinskii, V. K. 1987. "Hydrodynamics of explosions." Journal of Applied Mechanics and Technical Physics, vol. 28, No. 4, pp. 491-515, Plenum Publishing Corporation.

Kedrinskii, V. K. and Mader C. L. 1987. "Accidental detonation in bubble liquids." Shock Tubes and Waves, Hans Gronig, Ed., pp. 371-376, VCH, Aachen.

Kedrinskii, V. K. 1993. "Nonlinear problems of cavitation breakdown of liquids under explosive loading (review)." Journal of Applied Mechanics and Technical Physics, vol. 34, No. 3, pp. 361-377, Plenum Publishing Corporation.


Published: August 1996; WTEC Hyper-Librarian