This data publication provides data from 39 experiments performed in 2021 to 2022 in the Gas-mixing lab at the Ludwig Maximilian University of Munich (Germany). The experiments were conducted to investigate the charging and discharging potential of decompressed soda-lime glass beads in varying enveloping gas composition and two different transporting gas species (argon and nitrogen).
The experimental setup is a modified version of an apparatus first developed by Alidibirov and Dingwell (1996) and further modified by Cimarelli et al. (2014), Gaudin and Cimarelli (2019), and Stern et al. (2019) to enable the detection and quantification of discharges caused by the interaction of the discharging particles. The latest modifications enable the setup to perform experiments under gas-tight conditions allowing to test different atmospheric composition and pressure and to sample the gas within the particle collector tank.
The sample material was ejected from the autoclave into the particle collector tank that is insulated from the autoclave and works as a Faraday cage. Discharges going from the jet to the nozzle were recorded by a datalogger. Additionally, the ejection of the decompressed material was recorded by a high-speed camera. The gas composition in the collector tank was changed from air to CO2 and a mixture of CO2 and CO. The particle collector tank was conditioned in two different modes: purging three times the tank with the desired gas composition or three times of purging and applying a vacuum in between. Analysis of gas samples taken from the collector tank before conducting the experiments revealed that in both cases a complete removal of the air was not achieved, but significantly reduced by the evacuation-purging method. Two gases were used to pressurize the sample within the autoclave: Nitrogen and Argon. The experimental results were compared to previous experiments (Springsklee et al., 2022a; Springsklee et al., 2022b).
This data publication provides data from 96 experiments from 2020 to 2022 in the gas-mixing lab at the Ludwig-Maximilians-Universität München (Germany). The experiments were conducted to investigate the influence of grain size distribution, especially the influence of very fines [<10 µm] on the generation of experimental volcanic lightning (VL). The influence of grain size distribution was tested for three different materials. Experimental discharges during rapid decompression were evaluated by their number and their total magnitude. The three materials used in this study are a tholeiitic basalt (TB), industrial manufactured soda-lime glass beads (GB) and a phonolitic pumice from the lower Laacher See unit (LSB). The samples were sieved into several grain size fractions, and coarse and fines were mixed to test the influence of the added fines on the discharge behaviour. For the tholeiitic basalt, the coarse grain size fraction is 180-250 µm, for the glass beads 150-250 µm and for the phonolitic pumice, two coarse grain size fractions, 180-250 µm and 90-300 µm were tested.
The experiments were carried out in a new experimental setup, a modification of the shock tube experiments first described by Alidibirov and Dingwell (1996) and its further modifications (Cimarelli et al., 2014; Gaudin & Cimarelli, 2019; Stern et al., 2019). A mixture of coarse and fine sample material is placed into an autoclave and continuously set under pressure with argon gas up to the desired decompression pressure (⁓10 MPa). Then, rapid decompression is initialized, and the sample material is ejected from the autoclave through a nozzle into a gas-tight particle collector tank. The particle collector tank is insulated from the nozzle and the ground and serves as a Faraday cage (FC). All discharges going from the erupting gas-particle mixture, the jet, to the nozzle will be recorded by a datalogger. All the discharges measured during the first 5 ms of ejection were taken into the evaluation of the discharge behaviour. The raw signals of the experiments were evaluated by a processing code developed by Gaudin and Cimarelli (2019). Additionally, the jet behaviour was recorded by a high-speed camera: the gas-exit angle and the exit angle of the gas-particle mixture were determined. The background of the high-speed video was divided into a black side and a white side. The gas-exit angle and the exit angle gas-particle-mixture were determined as the mean of the deviation angle of a straight trajectory angle of both sides.
Explosive volcanic eruptions generate sound mostly in the infrasound (<20 Hz), but also in the acoustic (>20 and < 20k Hz) frequency range. Sound from volcanoes is recorded and used to describe quantitatively properties of the eruptive column, e.g. mass flux, and therefore it has monitoring purposes. However, a physical understanding of the underlying processes, their efficiency, and – maybe most importantly – the acting parameters like gas overpressure, absolute gas/magma volume, fragmentation depth and geometry of the plumbing system are unknown.
To shed light over the relationship between sound emissions and source conditions, we performed shock-tube experiments generating gas-only jets in an anechoic chamber testing the following conditions:
- 3, 4, 50, 75, 80 and 130 bar reservoir overpressure;
- 2.14 and 8.57 L/D non-dimensional reservoir volumes, where L is the length of the shock-tube reservoir and D the diameter;
- cylinder and two funnels with 15- and 30-degree flaring walls nozzle geometries.
The jets’ sound emissions were recorded with a near and far-field array composed of a total of 16 microphones.
This archive consists of the raw sound emission recording for the experiments performed. Thus, for each experiment, the user can access a single experiment. Each file is in CSV format. File names are self-explanatory following the format: Acoustic_[vent shape]_[pressure ratio]_[non-dimensional mass supply]_[YYYYMMDDTHHMMSS].csv. As an example, a user who wishes to access the data corresponding to an experiment performed at 50 bar, L/D 8, and a cylindrical nozzle will have to look for the file Acoustic_cyl_50bar_LD8_20160830T094809.csv. For detailed description, please refer to the associated data description pdf.
This data publication provides data from 42 experiments from 2018 and 2019 in the Fragmentation Lab at the Ludwig-Maximilians University Munich (Germany). The experiments were taken out to analyse the influence of the water content and the initial temperature of the pre-experimental sample on the produced electrification in rapid decompression, shock-tube experiments. All samples used in this study are 90-300 μm loose ash samples from the lower Laacher See unit.To carry out this study, we have built up on previous studies by Cimarelli et al. (2014) and Gaudin & Cimarelli (2019b, dataset to be found in Gaudin & Cimarelli, 2019a). A sample of loose ash gets placed in an autoclave. In our study, we have added water in some experiments. Also, a furnace was often used to heat the sample to up to 320 °C. After both water addition and heating, the autoclave gets pressurized using argon gas. Once a target pressure of 9 MPa is reached, the experiment gets triggered by rupturing metal diaphragms, which rapid decompresses the sample and ejects it into a collector tank. This collector tank is made out of steel and electrically insulated from its surrounding, thus working as a Faraday cage (FC), which is able to detect the net charge within at any point during the experiment. We detect discharges on that net charge up to 10 ms after the ejection of the particles.This dataset contains:- an overview .xlsx file (ExperimentOverview) containing key information for the 42 experiments used for analysis in this study- raw .csv files for all experiments- .pdf files showing the key elements of the analysed experiments, incl. data from Faraday cage and pressure sensorsFor more information please refer to the data description and the associated publication (Stern et al., 2019).
Series of experiments to assess the role of pressure, mass of particles, and grain size distribution in the generation of charges and discharges during shock-tube experiments. Experiments have been achieved between 2017 and 2018 in the facilities of Department of Earth and Environmental Sciences - LMU München.This dataset contains:- an excel spreadsheet summarizing the 63 experiments in the database with their main characteristics- a pdf file for each experiment, with the waveforms of the main instruments used in the experiment (Pressure sensors and Faraday cage) as well as ellaborated data (total amount of charges and discharges, discharge size distribution.