Tunnel Speed Research Articles

Aerodynamic performance and local flow field characteristics of pantograph during operation in subway tunnel

Subway trains running at high speed in tunnels are subject to aerodynamic forces that cause significant differences in contact force between the front and rear sliders and the catenary, leading to abnormal wear or overstandard arcing. This paper established and validated the aerodynamic numerical model of pantograph in the tunnel to investigate the pantograph's aerodynamic behaviour. Results indicate that: (1) The aerodynamic drag and lift of the front slider are greater than those of the rear slider by around 16N at a train speed of 120 KM/h. (2) Within the range of −2° to 5° of pantograph head pitch angle, the aerodynamic drag and uplift of the front slider increased by about 12% and 45%, respectively, while those of the rear slider increased by about 55% and 125%, respectively. (3) The aerodynamic drag and lift of the front and rear sliders are linearly proportional to the square of the train speed. The mathematical model of the aerodynamic force coefficient and aerodynamic force of the subway pantograph front and rear sliders is fitted, laying a solid foundation for the establishment of a pantograph-catenary coupling dynamic model under the action of aerodynamic force.

Multi-Step Prediction of TBM Tunneling Speed Based on Advanced Hybrid Model

The accurate prediction of tunneling speed in tunnel boring machine (TBM) construction is the basis for the timely adjustment of the operating parameters of TBM equipment to ensure safe and efficient tunneling. In this paper, a multi-step prediction model of TBM tunneling speed based on the EWT-ICEEMDAN-SSA-LSTM hybrid model is proposed. Firstly, four datasets were selected under different geological conditions, and the original data were preprocessed using the binary discriminant function and the 3σ principle; secondly, the preprocessed data were decomposed using the empirical wavelet variation (EWT) to obtain several subseries and residual series; then, Intrinsic Computing Expressive Empirical Mode Decomposition With Adaptive Noise (ICEEMDAN) was used to perform further decomposition on residual sequences. Finally, several subsequences were fed into a Long Short-Term Memory (LSTM) network optimized by the Sparrow Search Algorithm (SSA) for multi-step training and prediction, and the predicted results of each subsequence were added up to obtain the final result. A comparison with existing models showed that the performance of the prediction method proposed in this paper is superior to other models. Of the four datasets, the average accuracy from the first step prediction to the fifth step prediction reached 99.06%, 98.99%, 99.07%, and 99.03%, respectively, indicating that the proposed method has high multi-step prediction performance and generalization ability. In this sense, this paper provides a reference for other projects.

Numerical Simulation and Engineering Application of Temporary Stress Field in Coal Mine Roadway

The imbalance between excavation and mining is significant as it restricts the efficient development of coal resources. Slow tunneling speed is primarily due to the inability to concurrently conduct excavation and permanent support operations, and temporary support is considered a key solution to this problem. However, the mechanism by which temporary support affects the surrounding rock in unsupported are as remains unclear, hindering the assurance of stability in these areas and the determination of a reasonable unsupported span. To address this issue, this work proposed a stress distribution model as temporary support, elucidating the distribution law of support forces within the surrounding rock. By analyzing the stress differences between areas with and without temporary support, the stress field distribution characteristics of temporary support were determined. Subsequently, the evolution of stress and strain in the surrounding rock within unsupported areas was analyzed concerning changes in temporary support length, support force, and unsupported distance. The results indicated that, although temporary support does not directly act on unsupported areas, it still generates a supportive stress field within them. The maximum unsupported distance should not exceed 3 m, and there is a strong linear relationship between the optimal temporary support force and the unsupported span. Furthermore, the length of temporary support should not exceed 17 m from the tunnel face. The successful application of the shield tunneling robot system verifies that temporary support can ensure the stability of the surrounding rock in unsupported areas, confirming the validity of the temporary support stress distribution model. This research can be used to design and optimize cutting parameters and temporary support parameters, arrange equipment, and design and optimize tunnel excavation processes to achieve safe and efficient tunneling.

Effectiveness analysis of a novel rectangular tunnel boring machine with planetary transmission for box jacking

Traditional rectangular tunnel boring machines have low tunneling efficiency, poor soil mixing effects, which has hindered the construction of long-distance and large-section box jacking projects. To overcome these limitations, a new type of full-face excavation boring machine was developed based on a planetary transmission mechanism. This machine achieves full-face excavation by utilizing three eccentric cutter heads that revolve around both the central axis of the cutter plate and their individual shafts. The design methodology, feasibility, and principles of this new mechanism were introduced. Furthermore, a successful construction project of an underground highway passage in Japan was presented as a case study to demonstrate the design and application of this tunnel boring machine. The case details include the excavation face support mechanism, optimal cutter-head layout, obstacle removal strategies, and methods for reducing jacking resistance. Monitoring data from the project verified the applicability, reliability, and overall engineering performance of the rectangular shield machine developed using the planetary mechanism. This research demonstrates that the planetary transmission mechanism-based boring machine offers superior performance in terms of ground settlement and tunneling speed, potentially providing a comprehensive solution to the challenges in the development of rectangular shield machines for box jacking projects.

Research on TBM parameter optimization based on failure probability

This study addresses the over-reliance on operator experience in Tunnel Boring Machine (TBM) operations by proposing a failure probability-based decision-making method to enhance the scientific accuracy and reliability of construction decisions. In large deformation soft rock zones, TBMs are significantly affected by surrounding rock stress and deformation, which can lead to reduced tunneling speed or even shield jamming, severely impacting construction progress and safety. To reduce subjective biases in operator decision-making, this study combines the stress release coefficient with a failure probability model to establish a limit equilibrium equation. Using Monte Carlo simulations, failure probabilities under varying geological conditions are evaluated, and the optimal tunneling parameters are selected by analyzing the cumulative effect over time. Additionally, the study incorporates a Bayesian updating method, dynamically adjusting model parameters based on periodic monitoring data, further reducing uncertainty and improving the accuracy of the decision support system. The results show that while higher tunneling speeds increase the instantaneous failure probability, considering the cumulative effect over time, the overall failure index decreases with increased speed. Conversely, lower speeds result in a lower instantaneous failure probability but prolonged exposure to high-risk conditions increases the overall failure index. With this decision-making method, operators can quantitatively and in real-time adjust tunneling parameters under complex geological conditions, minimizing failure risks and improving construction efficiency.

Exploiting the Tunneling Coffee Ring Effect of Universal Colorimetric Nanomaterials for Ultrafast On-Site Microbial Monitoring.

The coffee-ring effect is an eye-catching circle originating from a material-suspended liquid droplet at a solid substrate after liquid evaporation, but the low speediness has restricted practical applications. When nanomaterial aqueous solutions are dropped onto porous nitrocellulose (NC), the liquid is immediately absorbed through the porous tunnels of paper fibers, and nanomaterials are rapidly enriched on the contact lines between droplets and membranes. We called this ultrafast variant of the coffee ring effect the "tunneling coffee ring" (TCR). When nanomaterial sizes are smaller than that of pores, a larger-diameter ring of nanomaterials quickly materializes. The real-time particle size-dependent TCRs and liquid diffusion rings exhibit a dual-ring pattern on the NC membrane. The tunneling speed of the capillary effect is so fast that the pattern appears within seconds. We apply the TCR effect as a size-surface affinity-particle/fluid separation sensor for bacteria. Dextran-modified Au and MoS2 nanostructures are proposed to be antibody-free microbe kits. Our TCR effect is used to distinguish between particles of different sizes and affinities, which are highly relevant in complicated systems without electricity and equipment in resource-poor settings.

Time delay of reflected and transmitted laser pulse at laser action on a dense plasma slab

The time delay phenomenon of reflected and transmitted laser pulse under the action of s-polarized laser radiation on a supercritical plasma slab is considered. The dependence of the time delay and peak intensity of reflected and transmitted signals on the slab thickness, plasma density, and angle of laser radiation incidence is investigated. It is shown that with increasing thickness of the plasma slab, the saturation of the transmitted signal delay time (Hartman effect) does not occur due to the exponential decrease in its intensity. The tunneling speed of the laser pulse energy through the slab of supercritical plasma is calculated, and it is shown that at large angles of laser radiation incidence, it can exceed the speed of light in vacuum.

Formation mechanism of micro-seismicity difference between rockbursts in deep-seated parallel tunnels

Deep-seated parallel tunnels are highly susceptible to rockbursts owing to the geological environment and engineering disturbances caused by adjacent tunnel excavations. However, accurately predicting these is challenging. The temporal and spatial characteristics of microseismic (MS) events and rockbursts in parallel tunnels can be jointly analyzed owing to their similar occurrence environments. However, although the left and right tunnels exhibited similar rockburst features during the construction of the Gaoloushan highway tunnel, noticeable differences in the MS events were observed. To clarify the cause of this phenomenon, the mechanisms of the influences of the buried depth, rock mass structure, hydrogeological conditions, construction parameters, blasting disturbance, and other factors on the MS activities of the left and right tunnels were investigated. Our findings suggested that the original geological occurrence environments, including the buried depth, rock mass structure, and hydrogeological conditions, were the primary reasons for the MS differences between the left and right tunnels. There was no obvious correspondence between the tunneling speed and evolution of the MS events. The influences of the section change and blasting on the MS anomaly were restricted by the geological environment and surrounding rocks. The results provide valuable insights into the effects of geological conditions and construction parameters on the formation mechanisms of rockbursts and MS events and may assist in developing an effective early warning strategy, as well as in preventing and controlling rockbursts in parallel tunnels or tunnel groups.

Experimental Study on the Distribution Law of Wind Speed in Rectangular Section Tunnels of Coal Mines

Ventilation is the cornerstone of coal mine safety production, and accurate monitoring of ventilation parameters is the fundamental guarantee for ventilation technology decision-making. A calculation model for the average wind speed line position in rectangular section tunnels of coal mines was established based on the Boussinesk theory and Prandtl turbulence theory to address the issue of difficulty in meeting decision-making needs in wind speed monitoring accuracy. The airflow field of rectangular section tunnels under different wind speed conditions was measured at the coal mine site, and the average position of the measured average wind speed line was obtained. The comparison and verification with the theoretical calculation results were carried out, with an absolute error of less than 5%.

Effect of plant shapes on sand transport rate and aerodynamic particle entrainment rate from the perspective of plant drag

Plant shape is an important factor affecting sand transport rate and aerodynamic particle entrainment rate. Two different types of flexible plant models (one is slender and the other has a large upper part and a small lower part) and a rigid tree-like plant model are selected with approximately zero basal-to-frontal area ratio. The sand transport rate, aerodynamic entrainment rate and shear stress partitioning on vegetated surfaces were measured under different plant densities and incoming wind speeds in a wind tunnel. The results show that the sand transport rate and aerodynamic entrainment rate on vegetated surfaces decrease with an increase in lateral cover and form drag of plant models. The relationship between sand transport rate, aerodynamic entrainment rate and drag parameter β (defined as the drag coefficient ratio of a plant model to the bare surface) is established by introducing the attenuation function of effective wind speed, which decays exponentially with an increase in lateral cover and linearly with an increase in drag coefficient ratio β. The present findings contribute to our understanding of how different vegetation types affect sediment transport rate and aerodynamic entrainment rate.

Predicting Model of Dual-Mode Shield Tunneling Parameters in Complex Ground Using Recurrent Neural Networks and Multiple Optimization Algorithms

Based on the left tunnel of the Liuxiandong Station to Baimang Station section of Shenzhen Metro Line 13 (China), a prediction model for the advanced rate of dual-mode shield tunneling in complex strata was established to explore intelligent tunneling technology in complex ground. Firstly, geological parameters of the complex strata and on-site monitoring parameters of EPB/TBM dual-mode shield tunneling were collected, with tunneling parameters, shield tunneling mode, and strata parameters selected as input features. Subsequently, the Isolation Forest algorithm was employed to remove outliers from the original advance parameters, and an improved mean filtering algorithm was applied to eliminate data noise, resulting in the steady-state phase parameters of the shield tunneling process. The base model was chosen as the Long-Short Term Memory (LSTM) recurrent neural network. During the model training process, particle swarm optimization (PSO), genetic algorithm (GA), differential evolution (DE), and Bayesian optimization (BO) algorithms were, respectively, combined to optimize the model’s hyperparameters. Via rank analysis based on evaluation metrics, the BO-LSTM model was found to have the shortest runtime and highest accuracy. Finally, the dropout algorithm and five-fold time series cross-validation were incorporated into the BO-LSTM model, creating a multi-algorithm-optimized recurrent neural network model for predicting tunneling speed. The results indicate that (1) the Isolation Forest algorithm can conveniently identify outliers while considering the relationship between tunneling speed and other parameters; (2) the improved mean filtering algorithm exhibits better denoising effects on cutterhead speed and tunneling speed; and (3) the multi-algorithm optimized LSTM model exhibits high prediction accuracy and operational efficiency under various geological parameters and different excavation modes. The minimum Mean Absolute Percentage Error (MAPE) prediction result is 8.3%, with an average MAPE prediction result below 15%.

Heat transfer mechanism and emergency operating speed of moving train fires in a metro tunnel

The primary strategy for a burning train in metro tunnels is to drive it out of the tunnel, or to the station or safe area ahead. However, the heat transfer mechanism and the emergency operating speed of moving train fires in tunnels have not been addressed. In this study, a 1:10 train-tunnel model was designed to conduct a series of moving model experiments. The results show that with the increasing train speed in tunnels, the flame height decreases, the flame width and length first increase and then decrease, and the flame tilt angle increases. The maximum temperature at the train top increases by 81.7 % when the train speed increases from 2 to 6 m/s. A piecewise model is proposed to predict the maximum temperature at the train top. The maximum temperature rise at the tunnel ceiling is 17.4 K and exponentially decreases with the train speed, posing a limited threat to the tunnel structure. The convective heat flux received by the train accounts for 82.1 %–94.4 %. The heat transfer between the train, tunnel and flame is codetermined by the train-tunnel aerodynamic effect and fuel-rich zone. The emergency operating speed of the train is suggested to be 22.8 km/h when the heat release rate is 7.5 MW. This study innovatively reveals the combustion behavior of moving train fires in a metro tunnel and proposes guidelines for determining the emergency operating speed of burning trains. The results can provide references for the fire safety design and running capacity improvement of metro trains.

Effect of in vivo implantation sites on the graft-to-bone osteointegration induced by gradient nanofibrous scaffolds

Gradient nanofibrous scaffolds hold great promise as viable ligament grafts to enhance graft-to-bone integration for long-term reconstruction of damaged anterior cruciate ligaments. However, the effect of in vivo implantation sites on graft-to-bone osteointegration induced by gradient scaffolds remains largely unexplored. Here, we systematically investigated the effects of nanofibrous scaffolds with fiber organization and nanoHA/BMP-2 gradients on graft-to-bone osteointegration by implanting them into tibial and femoral bone tunnels, respectively. The nanofibrous scaffolds were fabricated to possess gradient regions and uniform regions at two ends, and the gradient regions were implanted into femoral tunnels and tibial tunnels as two experimental groups. The biomechanical test showed that the ligament grafts broke in the intraarticular zone at 12 and 24 weeks of implantation, confirming a good biofixation between the grafts and bone tissues at both implantation sites of the tibial and femoral tunnels. Additionally, the gradient region of the ligament graft was found to enhance osteointegration and promote the formation of more secure graft-to-bone interfaces, as compared to uniform regions. In femoral bone tunnels, a relatively slow osteointegration process was observed even in the gradient region of the ligament grafts, which showed the formation of distinct fibrocartilage interfaces at 12 weeks and further evolved into mature bone tissues at 24 weeks. In tibial bone tunnels, higher nanoHA/BMP-2 content led to rapid penetration of newly-regenerated bone tissues in the gradient regions of the grafts at 12 weeks, followed by bone remodeling and complete integration with native tibial plateau at 24 weeks. These findings might provide new insights to develop biomimetic gradient scaffolds for matching the osteointegration process and speed in tibial and femoral bone tunnels.

An adaptive operating parameters decision-making method for shield machine considering geological environment

The performance of shield machine is sensitive to geological conditions and its operation depends on driver experience. Based on D-ResNet network and improved inertia weight adaptive constrained particle swarm optimization algorithm (IWACPSO), this study proposes an adaptive operating parameters decision-making method for shield machine considering geological environment. First, a novel D-ResNet network is proposed to establish the mapping models between geological type, operating parameters and tunneling speed, cutterhead torque, respectively. Then, we design the evaluation indicators of tunneling performance considering construction efficiency and considering both construction efficiency and energy consumption, respectively, and build the mapping model between operating parameters and performance evaluation indicators. On this basis, the optimization equation with operation parameters as control variables and improving tunneling performance as the goal is established. In order to solve the decision results of optimal operating parameters under various geological types, we present an enhanced inertia weight adaptive constrained particle swarm optimization algorithm. Finally, the proposed D-ResNet and IWACPSO-based decision-making method are verified by the actual construction data of subway project in Singapore. The results show that the R2 values of the proposed D-ResNet network for predicting the tunneling speed and cutterhead torque reach 0.98 and 0.96, respectively, which are much better than AdaBoost, support vector regression, multiple linear regression and deep neural network. The IWACPSO-based decision-making method could accurately solve the optimal solution of operating parameters, and the optimization time is much lower than that of ant colony algorithm, genetic algorithm and exhaustive method. Moreover, operation parameter decision-making method considering construction efficiency increased the tunneling speed by 61.02% on average, and the operation parameter decision-making method considering construction efficiency and energy consumption increased the tunneling speed by 59.55% on average, while the tunneling specific energy decreased by 20.50% on average compared with the former.

The Contribution of Ski Poles to Aerodynamic Drag in Alpine Skiing

The present study was designed to determine the contribution of the cross-sectional area of the ski poles (Sp) to the total aerodynamic drag during alpine skiing. At three different wind speeds in a wind tunnel, 10 skiers assumed typical alpine skiing postures (high, middle, and tuck), and their frontal aerodynamic drag was assessed with a force plate and their cross-sectional area, along with that of their ski poles, determined by interactive image segmentation. The data collected were utilized to examine intra-subject variation in Sp, the effects of Sp on the coefficient of aerodynamic drag (Cd), and the product of Cd and total cross-sectional area (Cd∙S. The major findings were as follows: (i) Sp ranged from 0.0067 (tuck position) to 0.0262 m2 (middle position), contributing 2.2–4.8% of the total cross-sectional area, respectively; (ii) Sp was dependent on wind speed in the high and middle positions; (iii) intra-subject variations ranged from 0.0018 m2 (27.6%) in the tuck position to 0.0072 m2 (30.5%) in the high position; (iv) Sp exerted a likely effect on Cd and Cd∙S. The extensive intra- and inter-skier variability in Sp can account for as much as ~5% of the total frontal cross-sectional area and future investigations on how elite skiers optimize their positioning of the poles in a manner that reduces aerodynamic drag are warranted.

Assessment of vibrations caused by simultaneous passage of road and railway vehicles

Although subways are usually near the roads, very few studies have been carried out to assess the vibration caused by the simultaneous passage of road and railway vehicles. This study investigates the influences of effective parameters on railway and road induced vibrations. To this end, the force time histories of road and railway vehicles were obtained from vehicle/pavement and vehicle/railway track interaction models. The force time histories were imported to a three-dimensional finite element model to obtain the vibrations. A comprehensive field test was carried out to assess the validity of the results obtained from the model. A parametric study was performed to investigate the effects of different parameters such as soil properties, speed hump characteristics, depth of subway tunnel and vehicle speed on the railway/road vehicles induced-vibrations. Moreover, a comparison/distinction was made between the vibrations caused by rail and road vehicles.

Intelligent dimming control and energy consumption monitoring system of tunnel lighting

To achieve energy saving and safe driving in a tunnel, this work proposes a tunnel intelligent dimming control and energy consumption monitoring system. Firstly, a dynamic predicted tunnel traffic volume is established to optimize the timeliness of the system tunnel traffic volume. Secondly, a backpropagation neural network-based dimming control model is constructed, in which the luminance outside the tunnel, traffic volume and vehicle speed serve as the input, and the luminance inside the tunnel is the output. This model is then combined with the established integrated closed-loop control model of the tunnel internal and external luminance to achieve continuous dimming control of the tunnel. Finally, an energy consumption monitoring system is designed with an energy monitoring unit. The designed system was implemented and tested for 63 days in the Yongtaiwen–Chayuanli (China) tunnel. Experiment results show that the designed system can automatically control the luminance of the tunnel lighting according to the luminance measured outside the tunnel, traffic volume and vehicle speed, thus achieving continuous dimming control. This significantly reduced the power consumption (by approximately 65%) whilst ensuring the safety of tunnel traffic.

Clogging Prevention of Slurry–Earth Pressure Balance Dual-Mode Shield in Composed Strata with Medium–Coarse Sand and Argillaceous Siltstone

The slurry–earth pressure balance dual-mode shield has an earth pressure balance (EPB) and slurry shield functions. Based on a shield tunnel project of Guangzhou Metro Line 12 in China, this study investigates the clogging prevention of a slurry–earth pressure balance dual-mode shield in a composed stratum with medium–coarse sand and argillaceous siltstone. The results show that the slurry mode was not applicable to the composed stratum with medium–coarse sand and argillaceous siltstone. The excavated soil accumulated easily in the slurry chamber, causing shield clogging. The total thrust force of the shield increased significantly, the tunneling speed gradually decreased to 0, and the torque of the cutterhead increased slightly after the slurry shield was clogged. The fluctuation in the total thrust force, the cutterhead torque, and the tunneling speed also increased significantly. The EPB mode is recommended for composed strata with medium–coarse sand and argillaceous siltstone. The dispersible foam agent and water needed to be used for soil conditioning. The injection amount of foam and water was determined according to the status of the mud discharged by the screw conveyor. Water absorption can be used to characterize the water absorption capacity of particles larger than 0.15 mm. The ideal soil state was that the consistency index of the particles smaller than 0.15 mm was less than 0.5 to prevent the EPB shield from clogging. The water absorption of soil with a particle larger than 0.15 mm should be removed when calculating the consistency index.

Pengkondisi Sinyal RTD Presisi pada Terowongan Angin Indonesian Low-Speed Tunnel

The temperature of the Indonesian Low-Speed Tunnel (ILST) wind tunnel test section was measured using a Pt100-type Resistance Temperature Detector (RTD) sensor. With the upgrade of the Indonesian Low-Speed Tunnel - Data Acquisition and Reduction System (ILST-DARS) using Ethernet communication, an integrated RTD linearization circuit was designed with the Conditioning Unit (CU) Mk3 to replace the Newport 267B 16-bit parallel and DAS-Hub as the current RTD interface. In this research, the design of the signal conditioner uses the RTD_Linearization_v7.xls program from Texas Instruments, the LTspice simulator software, and the AMP01E precision instrumentation amplifier. Based on the calibration results in the range of 20 – 50 0C, this signal conditioner has an average deviation value of 0.38 0C (1.31%). In the wind tunnel speed variation testing with a range of 30 – 65 m/s, the RTD signal conditioner had an average deviation of 0.41 K (0.14%). The Repeatability Test procedure was carried out at a wind speed of 65 m/s with an angle of attack for the test model from -90 to 200 and data were collected 10 times at each angle. The average deviation of temperature against variations in the angle of attack of the test model in this procedure is 0.25 K (0.08%) and the average deviation of wind speed against variations in the angle of attack of the test model is 0.03 m/s (0.04%).

Icing wind tunnel measurements of supercooled large droplets using the 12 mm total water content cone of the Nevzorov probe

Abstract. Supercooled large droplet (SLD) icing can occur behind the protected surfaces of an aircraft and create severe aerodynamic disturbances, which represent a safety hazard for aviation. Liquid water content (LWC) measurements in icing conditions that contain SLDs require instruments that are able to sample unimodal and bimodal droplet size distributions with droplet diameters from 2 to 2000 µm. No standardized detection method exists for this task. A candidate instrument, which is currently used in icing wind tunnel (IWT) research, is the Nevzorov probe. In addition to the standard 8 mm total water content (TWC) collector cone, a novel instrument version also features a 12 mm diameter cone, which might be advantageous for collecting the large droplets characteristic of SLD conditions. In the scope of the two EU projects, SENSors and certifiable hybrid architectures for safer aviation in ICing Environment (SENS4ICE) and ICE GENESIS, we performed measurement campaigns in SLD icing conditions in IWTs in Germany, Austria and the USA. We obtained a comprehensive data set of measurements from the LWC sensor, the 8 mm cone sensor and the 12 mm cone sensor of the Nevzorov probe, and from the tunnel reference instrumentation. In combination with measurements of the particle size distribution, we experimentally derive a collision efficiency curve that is based on a suitable functional form for the new 12 mm cone for median volume diameters (MVDs) between 12 and 58 µm and wind tunnel speeds from 40 to 85 m s−1. Knowledge of this curve allows us to correct the LWC measurements of the 12 mm cone (LWC12) in particular for the inevitably high decrease in collision efficiency for small droplet diameters. In unimodal SLD conditions, with MVDs between 128 and 720 µm, LWC12 generally agrees within ±20 % with the tunnel LWC reference values from a WCM-2000 and an isokinetic probe. An increase in the difference between LWC12 and the WCM-2000 measurements at larger MVDs indicates better droplet collection properties of the 12 mm cone. Similarly, the favorable detector dimensions of the 12 mm cone explain a 7 % enhanced detection efficiency compared to the 8 mm cone; however this difference falls within the instrumental uncertainties. Data collected in various bimodal SLD conditions with MVDs between 16 and 534 µm and LWCs between 0.22 and 0.72 g m−3 also show an agreement within ±20 % between LWC12 and the tunnel LWC, which demonstrates the suitability of the Nevzorov sensor head with the 12 mm cone for measurements of LWC in Appendix O icing conditions.