the above-mentioned work [10] our experimental data reported here demonstrate
that the buoyant plume top oscillates near the plume mean penetration height. In a
stratified fluid, these oscillations may lead to the generation of internal waves.
A similar phenomenon has been described by Karlikov and Trushina in Karlikov
[31, 32], where the jet impinging on the air-water interface generates surface waves.
The mechanisms of plume oscillations are discussed in section “Generation of
Internal Waves by Turbulent Buoyant Plumes”. We give an overview of the laboratory experiments and numerical works devoted to this problem and summarize
the results of the theoretical analysis by [10] and by Ezhova and Troitskaya [21].
Section “Structure and Energetics of Internal Waves” presents the results regarding
the structure and energetics of internal waves generated by the plumes from the
collector, including experimental data from LTST, results of numerical simulations,
and a theoretical description. Finally, Surface Manifestations of Internal Waves
focuses on the surface manifestations of internal waves (IW).
Generation of Internal Waves by Turbulent Buoyant
Plumes
Oscillations of fountains in a stratified fluid, i.e. in a system similar to a plume
interacting with a pycnocline are able to generate internal waves. This effect has
been first demonstrated experimentally in the experiments modelling wastewater
outfalls by Troitskaya et al. [39], Bondur et al. [10] (note that the Froude number of
a fountain in the pycnocline is of the first order of magnitude).
The flow from the collector of the disposal system has been modelled in the
LTST. The overall LTST dimensions are as follows: 20 m long, 4 m wide, and 2 m
deep [2]. The density stratification in the LTST is generated by means of liquid
heating and cooling by heat exchangers installed along the lateral boundaries of the
tank. The results on the formation of nonuniform vertical distribution of temperature in the LTST [10] were performed in two series of experiments in the LTST
with different thermocline depth. The distance from the middle of the thermocline
to the surface was 40–50 cm in one series of experiments (standard stratification)
and 13–15 cm in the other series (shallow thermocline). In the series of experiments
with a shallow thermocline, horizontal velocity at the surface was measured by
Particle Tracking Velocimetry (PTV). The experimental setup is shown in Fig. 2.
A collector was modeled by a metallic pipe, blocked at one end, with 5 holes on its
lateral surface. The pipe was located horizontally across the tank in the middle of it
at depth H from the surface. The axes of the holes were oriented horizontally. The
free end of the pipe was connected by a hose to a reservoir filled with alcohol
solution.
The temperature oscillations in the thermocline were measured using an antenna
of 13 temperature sensors (thermistors). The antenna was fixed on a special portable
track and could be placed at different distances from the collector model. The
Surface Manifestations of Internal Waves Induced …
69
that the buoyant plume top oscillates near the plume mean penetration height. In a
stratified fluid, these oscillations may lead to the generation of internal waves.
A similar phenomenon has been described by Karlikov and Trushina in Karlikov
[31, 32], where the jet impinging on the air-water interface generates surface waves.
The mechanisms of plume oscillations are discussed in section “Generation of
Internal Waves by Turbulent Buoyant Plumes”. We give an overview of the laboratory experiments and numerical works devoted to this problem and summarize
the results of the theoretical analysis by [10] and by Ezhova and Troitskaya [21].
Section “Structure and Energetics of Internal Waves” presents the results regarding
the structure and energetics of internal waves generated by the plumes from the
collector, including experimental data from LTST, results of numerical simulations,
and a theoretical description. Finally, Surface Manifestations of Internal Waves
focuses on the surface manifestations of internal waves (IW).
Generation of Internal Waves by Turbulent Buoyant
Plumes
Oscillations of fountains in a stratified fluid, i.e. in a system similar to a plume
interacting with a pycnocline are able to generate internal waves. This effect has
been first demonstrated experimentally in the experiments modelling wastewater
outfalls by Troitskaya et al. [39], Bondur et al. [10] (note that the Froude number of
a fountain in the pycnocline is of the first order of magnitude).
The flow from the collector of the disposal system has been modelled in the
LTST. The overall LTST dimensions are as follows: 20 m long, 4 m wide, and 2 m
deep [2]. The density stratification in the LTST is generated by means of liquid
heating and cooling by heat exchangers installed along the lateral boundaries of the
tank. The results on the formation of nonuniform vertical distribution of temperature in the LTST [10] were performed in two series of experiments in the LTST
with different thermocline depth. The distance from the middle of the thermocline
to the surface was 40–50 cm in one series of experiments (standard stratification)
and 13–15 cm in the other series (shallow thermocline). In the series of experiments
with a shallow thermocline, horizontal velocity at the surface was measured by
Particle Tracking Velocimetry (PTV). The experimental setup is shown in Fig. 2.
A collector was modeled by a metallic pipe, blocked at one end, with 5 holes on its
lateral surface. The pipe was located horizontally across the tank in the middle of it
at depth H from the surface. The axes of the holes were oriented horizontally. The
free end of the pipe was connected by a hose to a reservoir filled with alcohol
solution.
The temperature oscillations in the thermocline were measured using an antenna
of 13 temperature sensors (thermistors). The antenna was fixed on a special portable
track and could be placed at different distances from the collector model. The
Surface Manifestations of Internal Waves Induced …
69