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Sulfur dioxide is an ideal tracer to study the partitioning of the resistance of gas transfer across the water interface between air and water because the pH value in water controls the effective solubility of sulfur dioxide. Friman and Jähne (2019) already demonstrated that it is possible to measure sulfur dioxide concentration profiles with laser induced fluorescence (LIF), but the best excitation wavelength under standard atmosphericconditions was not known. Here, we report the result of our investigation to select the best excitation wavelength for sulfur dioxide fluorescence to reach maximum intensity with the lowest possible absorption.

Characterization of materials at interfaces includes also transfer processes taking place there. This is an ubiquitous phenomenon in the environment, technical processes, and living species. Because at least one of the two phases at the interface is mobile, these processes are characterized by a complex interplay between molecular diffusion and turbulent transport. In this paper, a new technique is introduced for fluorescence imaging of the mass transfer across the air-water interface.

In this presentation a new thermographic (non-invasive) technique for measuring the viscous shear stress in the water-sided boundary layer is reported. The method tags the water-sided flow with a heat profile induced by a laser line, and the temporal development of the heat profile is measured using a thermal camera. First results from pilot setups at the Heidelberg Aeolotron with a flat water surface as well as in the presence of wind generated waves show a good agreement with direct measurements of the velocity gradient in the water-sided viscous boundary layer using particle streak velocimetry.

Despite many field measurements of the gas transfer velocity, the measurements still show serious deficits. Mass balance methods suffer from large time constants and eddy covariance measurements from too low fluxes. Active thermography does not work either, because of the need to heat a too large patch at the water surface. Therefore the community is in need to develop improved or even better novel field measuring techniques. Given the fact that in reality the gas transfer velocity depends on other parameters than the wind speed, it is obvious that it will hardly be possible to infer more complex relations based on field data only. This emphasizes the importance of systematic wind-wave tank experiments to resolve the basic mechanisms under conditions which are as close to oceanic conditions as possible. The predictions gained from such investigations can then be tested with a small number of field experiments under well chosen environmental conditions.

In this presentation, the capabilities of the remodeled Aeolotron wind-wave tank at Heidelberg University, Heidelberg, Germany, are shown. It is argued, that, with the recent modifications, a realistic simulation of oceanic conditions can be achieved.

In this poster, it is argued, that bubble mediated gas transfer cannot explain the difference between DMS and CO2 observed in EC measurements.

The well established and worldwide used EMVA Standard 1288 for objective camera characterization is still limited to linear monochrome or color cameras without preprocessing. This paper previews the upcoming Release 4.0 which can characterize a much wider range of imaging sensors. This includes sensors with an extended spectral range — especially into the short-wave infrared (SWIR) —, multispectral sensors with more than three color channels, polarization sensors, time-of-flight sensors, high-dynamic range image sensors and any other sensor with a non-linear characteristic curve, and sensors with preprocessing in the camera in order to optimize image quality.

In November of 2014, air-sea gas exchange measurements using natural seawater taken from the North Atlantic were performed at the large annular wind-wave tank in Heidelberg, the Aeolotron, within the BMBF project SOPRAN (Surface Ocean Processes in the Anthropocene). Gas exchange experiments with of a large number of trace gases and volatile chemical species covering a wide range of solubility and diffusivity were conducted. Eleven different wind speeds, ranging from 1.5 to over 20 m/s, were used. Additionally, at three different wind speed conditions, a bubble generator was used to simulate the effects of strongly breaking waves with bubble entrainment. Measured gas transfer velocities are shown with special focus on the transfer velocities of gases with low solubilities, for which the transport process is water-side controlled. In addition, the dependency of the transfer velocities on the Schmidt number exponent is shown.

The exchange of gases across the air-water interface is described using the gas transfer velocity. Empirical models, which include the wind speed and the tracer's diffusivity to calculate the transfer velocity are state of the art. These simple, wind speed - gas transfer relationships work well for getting rough estimates of the gas transfer velocity, but they fail to catch the intricate interactions between the physico-chemical processes at play. Transfer velocities measured within the framework of the SOPRAN project at the Aeolotron wind-wave tank in Heidelberg during two extensive campaigns, including one with natural sea water, as well as during field experiments using active thermography in the Baltic Sea indicate, that the variability of the transfer velocity at a given wind speed is very large. Future air-sea gas exchange models must take the water surface characteristics such as the degree of coverage with surface active materials and a Schmidt number exponent varying between 2/3 and 1/2 into account.

Gas transfer velocities were measured in two high-speed wind-wave tanks (Kyoto University and the SUSTAIN facility, RSMAS, University of Miami) using fresh water, simulated seawater and seawater for wind speeds between 7 and 85 m s−1. Using a mass balance technique, transfer velocities of a total of 12 trace gases were measured, with dimensionless solubilities ranging from 0.005 to 150 and Schmidt numbers between 149 and 1360. This choice of tracers enabled the separation of gas transfer across the free interface from gas transfer at closed bubble surfaces. The major effect found was a very steep increase of the gas transfer across the free water surface at wind speeds beyond 33 m s−1. The increase is the same for fresh water, simulated seawater and seawater. Bubble-induced gas transfer played no significant role for all tracers in fresh water and for tracers with moderate solubility such as carbon dioxide and dimethyl sulfide (DMS) in seawater, while for low-solubility tracers bubble-induced gas transfer in seawater was found to be about 1.7 times larger than the transfer at the free water surface at the highest wind speed of 85 m s−1. There are indications that the low contributions of bubbles are due to the low wave age/fetch of the wind-wave tank experiments, but further studies on the wave age dependency of gas exchange are required to resolve this issue.

A newly developed laser-induced fluorescence technique to measure high-resolution vertical concentration profiles of the tracer sulfur dioxide above the air-water interface is presented. The concentration profiles can be used to study the transport mechanisms in the air-sided boundary layer at a wavy interface including the gas transfer velocity, turbulent concentration fluctuations, and the partitioning of gas transfer between air and water. The imaging technique was tested in a wind-wave facility under invasion conditions. A proof of principle is presented as well as a first evaluation of the capabilities and uncertainties of the method. In combination with particle imaging velocimetry, this measurement technique will allow for a detailed study of the transport processes across the mass boundary layer., {"references":["Krall, K., 2013. Laboratory Investigations of Air-Sea Gas Transfer under a Wide Range of Water Surface Conditions. PhD Thesis, University of Heidelberg.","Deacon, E. L., 1977: Gas transfer to and across an air-water interface. Tellus A, 29, pp. 363–374.","Kühlein, F., 2019. Vertikaler Impulstransport bei kleinen Windwirklängen in einem linearen Wind-Wellenkanal. BSc Thesis, University of Heidelberg."]}

Heat transfer velocities measured during three different campaigns in the Baltic Sea using the active controlled flux technique (ACFT) with wind speeds ranging from 5.3 to 14.8 m s−1 are presented. Careful scaling of the heat transfer velocities to gas transfer velocities using Schmidt number exponents measured in a laboratory study allows us to compare the measured transfer velocities to existing gas transfer velocity parameterizations, which use wind speed as the controlling parameter. The measured data and other field data clearly show that some gas transfer velocities are much lower than those based on the empirical wind speed parameterizations. This indicates that the dependencies of the transfer velocity on the fetch, i. e., the history of the wind and the age of the wind-wave field, and the effects of surface-active material need to be taken into account.

This project aims at imaging gas concentration profiles with Laser-Induced Fluorescence of sulfur dioxide in invasion experiments in a wind-wave tunnel for investigations of the air-sided mass boundary layer and the gas transfer velocity. The technique will allow for contactless high resolution eddy covariance measurements in the laboratory., {"references":["Deacon, E. L., 1977: Gas transfer to and across an air-water interface. Tellus A, 29, pp. 363–374.","Krall, K., 2013. Laboratory Investigations of Air-Sea Gas Transfer under a Wide Range of Water Surface Conditions. PhD Thesis, University of Heidelberg.","Buckley, M.P. and Veron, F., 2016. Structure of the airflow above surface waves. Journal of Physical Oceanography, 46(5), pp.1377-1397."]}

Measuring the transfer of trace gases across the air-sea boundary at hurricane wind speeds in the field is extremely challenging and dangerous. Therefore, the Kyoto High Speed Wind Wave Tank and the Miami SUSTAIN wind-wave tank with wind speeds between 7 and 78 m/s were used to measure the gas transfer velocities of a multitude of tracers (including He, SF6, and DMS) spanning a wide range of solubilities and Schmidt numbers. Results obtained from three different campaigns are presented, where gas transfer velocities were measured with sea water, fresh water as well as with fresh water containing trace amounts of Butanol (simulated sea water), which changes the bubble spectrum to be comparable to that of salt water. A new regime, in which the gas transfer velocity increases stronger than the friction velocity to the third power, starting at a wind speed of around 35m/s was found. In fresh water, bubble-mediated gas transfer contributes at most one third to the total gas transfer velocity even for the gases with the lowest solubilities (He and SF6). But the same steep increase of the gas transfer velocity is found for moderately soluble volatile compounds, where bubble contribution is negligible. Therefore, this strong increase is not caused by bubble-induced gas transfer. For simulated sea water and sea water, bubbles contribute up to two thirds to the total gas transfer for gases with low solubilities. However, for gases with dimensionless solubilities larger than one, bubble contribution is not significant. High-speed image sequences of the water surface at hurricane wind speeds give a first indication of the mechanisms taking place. The steep increase in the gas transfer velocity is likely caused by a combination of strongly enhanced turbulence at the water surface and the enlargement of the water surface itself by various processes such as bag breakup, projections and bubbles bursting through the water surface. Further investigations are required to quantify these processes and their contribution to gas transfer in more detail., The video sequence from slide 21 can be found at: https://youtu.be/GQmHN8Bz2r0 and the video from slide 35 can be found at: https://youtu.be/DUrP-rRnRxU

The exchange of trace gases such as carbon dioxide or methane between the atmosphere and the ocean plays a key role for the climate system. However, the investigation of air–sea gas exchange rates lacks fast and accurate measurement techniques that can also be used in the field, e.g., onboard a ship on the ocean. A promising way to overcome this deficiency is to use heat as a proxy tracer for gas transfer. Heat transfer rates across the aqueous boundary layer of the air–water interface can be measured via thermography with unprecedented temporal and spatial resolution in the order of minutes and meters, respectively. Either passive or active measurement schemes can be applied. Passive approaches rely on temperature differences across the water surface, which are caused naturally by radiative and evaporative cooling of the water surface. Active measurement schemes force an artificial heat flux through the aqueous boundary layer by means of heating a patch at the water surface with an appropriate heat source, such as a CO2 laser. The choice of the excitation signal is crucial. It is beneficial to apply periodic heat flux densities with different excitation frequencies. In this way, the air–water interface can be probed for its response in terms of temperature amplitude and phase shift between excitation signal and temperature response. This concept from linear system theory is also well established in the field of non-destructive material testing, where it is known as lock-in thermography. This article gives a short introduction into air–sea gas exchange, before it presents an overview of different thermographic measurement techniques used in wind-wave facilities and at sea starting with early implementations. The article closes with a novel multifrequency excitation scheme for even faster measurements.

Lecture given on October 25, 2017 at the Fraunhofer-Allianz Vision Technologietag 2017, Jubiläumskongress 20 Jahre Fraunhofer Vision

Following the 2nd European Machine Vision Forum of the European Machine Vision Association (EMVA) in Vienna from September 6-8, 2017, it is argued that collaboration between industry and academia is now more important than ever., www.imveurope.com

High-end scientific CMOS (sCMOS) sensors with a linear characteristic have reached already a quality level that 16-bit quantization is required in order to resolve the low temporal noise level in the dark image. Further progress will sooner or later require a quantization resolution of more then 16 bits. This poster descibes that the signals of linear image sensors with high dynamic range and large maximum SNR, can be represented with a bit resolution far below 16 bit, keeping the processing fast. In addition, a non-linear gray value scale with gray-value independent temporal noise is advantageous for almost any type of image processing except radiometric evaluation. For the latter it is easy to linearize the signal again by applying the inverse gray value transform.

From ancient times, science has always used images to document observations and results. In the beginning, people made sketches and drawings, but in the mid-19th century, the advent of photography revolutionised the way we use visual documentation. For the first time, images could be recorded objectively. The quantitative analysis of the photographs, however, was a time-consuming manual task, which restricted analysis. Today we are experiencing a second revolution: Modern cameras record digital images that are subsequently analysed by powerful computers. Image processing has become an indispensable part of any modern quantitative science – it is the means of choice when it comes to the capture and quantitative analysis of complex processes that vary in time and space. Such complex processes are encountered in environmental science. One research topic at the Heidelberg Institute of Environmental Physics is the question of how environmentally relevant trace gases are exchanged between the atmosphere and the world’s oceans. The ‘bottleneck’ for the transport of trace gases from the atmosphere into the sea is a boundary layer of surface water that is only 20 to 200 micrometres thick. The processes taking place in this agitated boundary layer are investigated by environmental researchers in cooperation with the Heidelberg Collaboratory for Image Processing (HCI) at the Interdisciplinary Center for Scientific Computing (IWR). Together the scientists developed a number of new methods to visualise these complex transactions and to process the resulting image sequences. The new methods allow them to measure not only water waves generated by the wind and the bubbles introduced to the water by breaking waves, but also the current near the water surface and concentration fields of dissolved gases in the thin boundary layer. In this way, the mechanism of air-water gas transfer can finally be understood.

EMVA 1288 datasheet m0727 Basler acA1920-155um monochrome SN 21735903 with Sony Pregius CMOS sensor IMX174, exposure time 0.5 ms, gain 0.0 dB

EMVA 1288 datasheet m0728 Basler acA1920-155um monochrome SN 21735903 with Sony Pregius CMOS sensor IMX174, exposure time 0.5 ms, gain 12.0 dB

EMVA 1288 datasheet m0791 Basler acA2500-14gm monochrome SN 21130884, 50 ms exposure time, 14.1 fps including spectroscopic quantum efficiency measurements with 3 nm resolution

EMVA 1288 datasheet m0637 IDS UI306xCP-M monochrome SN4102839784 with Sony Pregius CMOS sensor IMX174, 0.5 ms exposure time, minimum gain.

EMVA 1288 datasheet m0774, PCO edge5.5 USB 3.0 monochrome, SN 61000057, 1.0 ms exposure time, 30.41 fps including quantum efficiency measurements with 3 nm resolution. HDR measurements covering a dynamic range of about 5000.

EMVA 1288 datasheet m0790 Basler acA640-120gm monochrome SN 21390799, 20 ms exposure time, 50 fps, including spectroscopic measurements of quantum efficiency with 3 nm resolution.

EMVA 1288 datasheet m0791 Basler acA2500-14gm monochrome SN 21130884, 1.715 ms exposure time, 14.1 fps including spectroscopic quantum efficiency measurements with 3 nm resolution

EMVA 1288 datasheet m0773, PCO edge5.5 USB 3.0 monochrome, SN 61000057, 30 ms exposure time, 30.41 fps including quantum efficiency measurements with 3 nm resolution

Experiments in the new wind/wave facilities in conjunction with novel experimental techniques have a high potential to make a significant contribution to the understanding of air-sea gas transfer and other small-scale air-sea interaction processes.

Active thermography has been used for almost 30 years to explore air-sea gas transfer both in laboratory and field experiments. In the early 2000s, some doubt arose whether it was possible to extrapolate heat transfer velocities to gas transfer velocities. Because of the large difference in the molecular diffusivity, different mechanisms may govern the transfer of heat and mass. However, in a recent experimental study at the large annular wind-wave tank in Heidelberg, the Aeolotron, Nagel et al. [2014] could show that heat transfer velocities can be scaled to gas transfer velocities with an accuracy of better than 10%, provided the Schmidt number exponent is known. These measurements were performed using the original active thermographic technique proposed by Jähne et al. [1989], by heating a rather large area at the water surface of up to one square meter. This is required to ensure that water parcels stay longer in the heated patch than the response time of heat transfer across the boundary layer. The setup used by Nagel et al. [2014] still had one disadvantage. The heated patch showed some inhomogeneity in cross-wind direction, caused by the method to expand the beam of the CO2 laser. By using a holographic beam expander, a much more homogeneous irradiation could be achieved. With this improvement it was possible to acquire significantly more accurate heat transfer measurements. In November 2014 this technique was used in air-sea gas exchange measurements using natural seawater from the North Atlantic with various degrees of contamination by natural surface films at the Heidelberg Aeolotron, within the BMBF project SOPRAN (Surface Ocean Processes in the Anthropocene). First results from this experiment will be shown. &nbsp

This work presents a novel laser-induced fluorescence (LIF) technique to visualize two-dimensional water-sided oxygen concentration fields in cross-wind direction measured in a linear wind-wave facility in order to study the cross-wind spatial structures of the concentration field, which might be influenced by micro Langmuir circulation or other coherent turbulent structures. The oxygen quenching technique was applied to visualize oxygen concentrations in water. The technique takes advantage of the fact that the photon flux, emitted by a fluorophore, which is solved in the water, decreases in the presence of oxygen molecules. The relation between the oxygen concentration and the photon flux is described by the modified Stern-Volmer equation for high laser irradiance.

The Heidelberg Aeolotron is an annular wind/wave facility with 10m diameter. One of the main advantages in contrast to a linear facility is the nearly infinite fetch. The conditions on the water surface, and so the gas transfer are more similar to conditions at the open ocean. The wind field in the Aeolotron was investigated with a pitot tube mounted on a translation stage. The radial wind speed was measured for a complete cross section at ten positions. To measure near the water surface surfactants were added to dampen the wave field. Because of the inhomogeneous wind field and secondary currents due to the annular geometry the friction velocity u* cannot be determined by the logarithmic wind profile. But as an advantage of the annular geometry the momentum balance in water can be used to get u*. Using the increase of the water velocity after turning on the wind, the friction at the walls and u* can be determined. An acoustic velocity sensor was used during a large number of experiments to quantify the friction at the walls. We found a dependence on the mean water velocity and on wave motion, which we parametrized. Together with the velocity in equilibrium, the wind induced friction velocity was determined for a large range of wind speeds up to 10m/s. Additional experiments with two concentrations of the surfactant Triton X-100 show the influence of different wave fields on the friction velocity. The annular geometry generates secondary currents in water, too. This could be quantified at the Aeolotron by measuring the 3D water velocity in a cross section. The cross wind velocity components account for up to 10% of the mean flow at medium wind speeds.

Therefore a new modified LIF technique has been developed for the visualization of simplified turbulence structures of the aqueous mass boundary layer. The technique is based on a system of chemical reactions to feature binary concentration fields. With penetrating through air-water interface, an alkaline tracer gas (in current studies - ammonia) changes a temporal equilibrium of chemical species in the water that defines local [H+] concentration. A shift in [H+] concentration, consequently a shift in pH value can be captured with high resolution imaging by the use of fluorescent pH indicator Pyranine (8-hydroxy-1,3,6-trisulfonated pyrene). More importantly, logarithmic dependence of the pH value on [H+] concentration provides a rapid increase of pH value that insures sharp change in fluorescent component of Pyranine, hence proximate binary fluorescent field. This contribution reports two pieces of work. Firstly test experiments were performed at the small Benjamin linear wind-wave tunnel in order to verify the technique and to set it up in an optimum way. Secondly, an approach is introduced to reconstruct 3D- image sequences in order to fully capture the spatio-temporal turbulent structures in the mass boundary layer. In the Benjamin facility a vertical laser beam at 445 nm was focused to excite Pyranine fluorescence. To capture one dimensional profiles with a high resolution of 4.4 μm, tilted sided-placed Basler ace acA2500-14gm cameras with 2.2 μm pixel size were operated in 320 Hz mode. Experimental 1D concentration profiles at different conditions were analyzed with defining the range of ammonia and Pyranine concentrations as well as initial conditions to maintain in order to gain binary concentration fields. At the different wind speed the experimental profiles were evaluated to estimate the thickness of the mass boundary layer and to detect boundary layer detachments (surface renewal events). The profiles were also compared to simulation profiles for different gas exchange models to verify the case of simplified binary fields and to understand the behavior of fluorescence within the mass boundary layer. Secondly, a trinocular setup was tested for high-resolution 3D-reconstruction of sequences of boundary layer images at the large annular Aeolotron wind-wave facility in Heidelberg. In contrast to the setup of [Kräuter et al., 2014] three low noise CMOS cameras were placed underneath the facility. An example of captured images from cameras placed 25 cm apart from each other is presented in Fig. 2. The next step of presented work will be the reconstruction of captured 2D-projections to 3D space. &nbsp

An experimental study for the investigation of bubble-mediated gas exchange in a dedicated bubble tank is presented. Bubbles were generated by a water jet with adjustable kinetic energy, which entrained a controllable gas volume flux into the water tank. Bubble size distributions in a radius range from 10 μm to 5000 μm and velocity distributions in a range from 70 μm to 3000 μm were measured at 60 positions in the tank by a telecentric optical setup. Trace gas concentrations were measured using a quadrupole mass spectrometer with a silicone membrane inlet in the water phase of a gas tight bubble tank. Fourteen trace gases with a wide range of solubilities and diffusivities - SF6, Ne, N2 ,HD, D2, O2, Kr, Pentafluoroethane, Xe, N2O, C2H2 , CH3Cl, Benzene and DMS - were used to investigate the dependency on these two physico-chemical parameters. Evasion experiments with a variety of conditions were conducted, including salt water (1.75 % NaCl), the addition of the soluble surfactant Triton X- 100, n-butanol and glycerol. All used additives tend to increase the fraction of small bubbles generated and therefore increase the transfer velocity at constant gas volume flux and energy input. The addition of salt had the strongest effect, leading to an enhancement of the transfer velocity up to a factor of ~4. The increase of the transfer velocity adding Triton X-100 was found to be lower than 5 %. The transition between diffusivity controlled and solubility controlled transfer occurs at solubilities ranging from 0.05-0.44. The transition is shifted to lower solubilities by a factor of ~3 by the addition of salt. Existing models for bubble mediated gas transfer are tested. Simple power law dependencies turn out to be incapable to describe the transfer for the whole range of solubilities and diffusivities. An extension of the parameterization proposed by Woolf et al. (2007) requiring 4 parameters fits the data best. A simple model using only 2 parameters is proposed. Its performance is almost as good as the extended Woolf model.

EMVA 1288 datasheet m0553 Basler acA4600-10uc, SN 21548908

EMVA 1288 datasheet m0545, Basler acA3800-14um, SN 21529784

EMVA 1288 datasheet m0550, PCO edge5.5 USB3.0 monochrome, SN 61000057

Description of the large wind-wave facility of Delft Hydraulics, The Netherlands

The exchange of trace gases across the air-sea boundary layer is characterized by the gas transfer velocity k = 1/β u* Sc-n,with the friction velocity u* (a measure for momentum input into the water), the tracers Schmidt number Sc, and the Schmidt number exponent n which changes gradually from n=2/3 for a smooth water surface, to n=1/2 for a rough and wavy surface. β denotes the momentum transfer resistance, a dimensionless scaling parameter. In recent years, many new insights into the transition of the Schmidt number exponent n from smooth to rough conditions were acquired in detailed lab studies, while there is a lack of studies focusing on β. Using experimental data from various wind-wave tank laboratories, we found that β, just like the Schmidt number exponent n, is not a constant but depends on the state of the water surface as well as the degree of contamination of the water surface with surface active material.

For the first time, air-sea gas exchange measurements under the influence of four surface active substances also found in the sea surface microlayer were performed in the Aeolotron wind-wave tank. Chosen surfactants were Dextran which is water soluble, as well as the insoluble substances Mono-Galactosyl-Diacylglycerol, Palmitic Acid and Phosphatidylglycerol. Gas transfer velocities of N2O and C2HF5 were measured using a mass balance approach combined with FT-IR spectroscopic methods. In addition, wave parameters like the mean square slope of the water surface were monitored. It was found that Dextran alone does not significantly decrease the gas transfer velocity compared to the clean water surface, while reduction for the full mix of surfactants was as high as 70%. For the full mix of surfactants, at a wind speed of around 7m/s the surfactant film ruptured and was mixed down into the water bulk where it was inefficient in suppressing gas transfer.

Proposes a new experimental approach to determine diffusion coefficients and solubility of volatile chemical species simultaneously by gas transfer measurements in a small gas-tight tank.

A novel 2-D fluorescence imaging technique has been developed to visualize gas exchange between air and water using ammonia as a tracer. Fluorescence is stimulated by high-power LEDs and is observed from above with a low-noise, high-resolution and high-speed camera. The invasion of ammonia into water leads to an increase in pH (from a starting value of 4), which is visualized with a fluorescent dye. The flux of ammonia can be controlled by controlling its air-side concentration. A higher flux leads to an increase of the thickness of the layer, from which fluorescent light is emitted (pH > 7). In this way, a varying fraction of the thickness of the aqueous mass boundary layer is imaged. In addition to the fluorescence measurement, we conducted collocated and simultaneous thermography and wave imaging measurements. With this data set, it is possible to compare heat and gas transfer and to investigate the effect of waves on both transfer processes. First results will be presented.