Hideo Ohashi, Prof. Emeritus

University of Tokyo & Kogakuin University
The Window to Society after Retirement from Engineering Education


 This top page is to transmit the proof that I am still alive and enjoying retired life, mainly to my relatives, friends and former students. A story or an event is selected from daily life and my thoughts and experience are introduced.

From Daily Life - 83: Tunnel ventilation

 During traveling by train or car, we often pass through tunnels. Unless the tunnel is very long, we pass through it almost unconsciously. My longtime friend, Mr. N, founded a company specialized in ventilation and safety equipment for automobile tunnels and celebrated its 25th anniversary this year. I was invited to the anniversary event to give a congratulatory speech, and it reminded me of my 40 years of commitment to the planning of major automobile tunnels in Japan. On this occasion, I introduce herewith briefly what tunnel ventilation is.
 With the advancement of railway electrification, railway tunnels with ventilation equipment are rare, except for subways. In the case of the longest railway tunnel in Japan, Seikan Tunnel (54 km), fresh air is supplied from two inclined shafts to its center to regulate the internal temperature and allow safe evacuation in the event of a fire. This is a special case because of its length and undersea condition.
 In automobile tunnels, ventilation must always be considered because it is necessary to dilute the pollutants emitted by engines (harmful gases such as carbon monoxide and nitrogen oxides and diesel soot) under the permissible limit. Harmful gases are toxic to the health of pedestrians through breathing, and diesel soot poses a risk to drivers by reducing visibility.
 Pollutants emitted inside a tunnel are carried to the outside by natural wind due to the difference in atmospheric pressure between the portals, traffic wind pushed by running automobiles, and diffusion caused by strong air turbulence generated by cars passing by. If these effects are strong enough, mechanical ventilation is not necessary. Most of short tunnels under 500 meters fall into this category.
 When a construction plan for an automobile tunnel over 500 meters is decided, the need for ventilation and safety equipment is determined, taking into account the traffic volume, one- or two-way, terrain conditions, and environmental regulations near the portals.
 In the past, automobiles were a major source of public nuisance. However, due to successive tightening of exhaust gas regulations, the emission of pollutants from both gasoline and diesel vehicles has decreased dramatically in recent years. As electric vehicles become more widespread, the emission of pollutants will decrease even further. For this reason, tunnel ventilation facilities are often installed not for diluting pollutants but to ensure the airflow necessary for safe evacuation in the event of a fire. Recently, we see many tunnels with jet fans installed on the ceiling (photo upper right), but it is rare to see fans that are in operation.
 Ventilation fans are regularly in operation in long tunnels such as Kan'etsu Tunnel (11 km, photo upper left), Enasan Tunnel (7 km), and Tokyo Bay Aqua Tunnel (10 km). In the past, long tunnels were mostly mountain tunnels. However, as construction of underground expressways in urban areas progresses, they become the record holder of the longest automobile tunnel. Currently, Yamate Tunnel (19 km) on the Metropolitan Expressway holds the record. Automobile tunnels have become more familiar as they feel like subways.
 Automobile tunnels have a history of serious accidents that have cost lives, such as the fire at Nihonzaka Tunnel and the ceiling panel collapse at Sasago Tunnel. I hope that the ventilation and safety equipment of automobile tunnels will keep assuring the safety of passersby for years to come.



→ Past Top Pages

   
"From Daily Life"
        
1: Tracing family roots
        
2: The second last car
        
3: August 15. my memorial day
        
4: Battlefield rations
        
5: Begginer at the gym
        
6: Fuji View Hotel
        
7: Lesson in Hiragana writing by brush
        
8: Moving from old to new smartphone
        
9: Living alone in my second year
        
10: Welcomed by cherry blossom
        
11: Eden of peach blossom
        
12: Tama River Walk
        
13: Chichibu Pilgrimage
        
14: Bonds with local community
        
15: About my homepage
        
16: Annual report of athletic gym
        
17: Pilgrimage to Mt. Tsukuba
        
18: Reunion of alumni and classmates
        
19: Braking by left foot
        
20: Battlefield rations in the sequel
        
21: Granddaughter has come!
        
22: Visit to Kobayashi Residence
        
23: Wake-up exercise
        
24: Digital photo album
        
25: Seven tools for brushing teeth
        
26: Ambulance
        
27: Quick report on drive monitoring
        
28: Hearing aid
        
29: Jindai Botanical Park
        
30: 2020, a historic year
        
31: Topics of eye
        
32: Final report on drive monitoring
        
33: Cognitive ability test
        
34: PCI to prevent heart infarction
        
35: Ashikaga Flower Park
        
36: 90 years old supported by medication
        
37: 3 years with Subaru
        
38: 45 years living in Seijo
        
39: Caspian Sea yogurt
        
40: Home Museum of Aunt Zschäbitz
        
41: Reunion of university classmates
        
42: Okutama spar tour
        
43: New Year's greeting card
        
44: Implant
        
45: Fuchu Forest Park
        
46: Grave closing
        
47: Walking group of local community
        
48: How-to books for the elderly
        
49: Home altar
        
50: Such a life
        
51: Knee of the elderly
        
52: Metropolitan Kinuta Park
        
53: Shirakaba Art Museum of Kiyoharu
        
54: Haiku; Metasequoia
        
55: Three years with COVID-19
        
56: Battlefield rations in the 6th year
        
57: Hearing impairment
        
58: Shinjuku Station
        
59: Haiku with photograph
        
60: Moving to 5G smartphone
        
61: History of private cars
        
62: Setagaya Art Museum
        
63: FreeCell
        
64: Turbo
        
65: Hinata Temple of Yakushi
        
66: Moving of home computer
        
67: Amakusa tour
        
68: Hand craft as a hobby
        
69: Kitami Community Square
        
70: Photo-Haiku 2
        
71: Support scam abusing Trojan Horse
        
72: Bedside gym
        
73: Metropolitan Nogawa Park
        
74: Family funeral
        
75: Sudoku (Number Place)
        
76: Photo-Haiku 3
        
77: Ohyama Afri Shrine
        
78: Kunisaki Peninsula tour
        
79: The old school system is far away
        
80: Cooking group of local community
        
81: Motor fan group of local community
        
82: Directories disappear!

   
"Memorable Scenes"
          Series 1: Parade with Doctor hat on the head
          
Series 2: Calligraphy in a frame
       
Series 3: A young man from the Orient
        Series 4: Sumo-stamping
        Series 5: Waiting room of Shanghai Station
        Series 6: Let's Walk Festival
       
Series 7: Last long-distance drive
          Series 8: My Car No. 3
          
Series 9: Ski camp
          
Series 10: Safari experience
        
Series 11: First encounter with dogwood
        Series 12: Mt. Fuji

   
"Treasure Box of Words"
          Series 1: Virtue brings profit
          Series 2: Wait for a ripe moment
          Series 3: Catch the symptoms
          Series 4: Words are selected metaphors
          Series 5: Start with two humans
          Series 6: Optimism is a will, pessimism a mood
          Series 7: Atop a summit, and another becomes visible
          Series 8: We see only what we want to see
        Series 9: Chanllenge is the privilage of the young
        Series 10: Today is the first day of my life

   
Engineer Series 1: Who's engineer, juveniles' answer
          Series 2: Corus of "We raise engineers!"
          Series 3: From Nobel Prize to Gold Medal
          Series 4: Professionals in three categories
          Series 5: Various tasks in engineering
          Series 6: Classification of EPs by IEA
          Series 7: Science, technology and related professionals
          Series 8: Proposal for the classification of engineers
          Series 9: Revised proposal for the classification of engineers
          Series 1 - 10: Whole Series including summary and remarks

    Cartoon Series 1: Mechanism of viscosity
          Series 2: Mechanism of loss generation
          Series 3: Commuter packer and enthalpy
          Series 4: Skinny grasshopper and fat pupa
          Series 5: From hand-drawn picture to ready-made clip art
          Series 6: Why do you learn? - 1
         
Series 7: Why do you learn? - 2
          Series 8: Two Sciences
         
Series 9: Scientist and Engineer
          Series 10: Science and Non-science
        Series 11: Structure of human relations
        Series 12: Oriental subconsciousness

   
Nostalgia Series 1: The first own car
          Series 2: The first driver's license
          Series 3: Comparison of German and Japanese Diploma
          Series 4: The first air travel
          Series 5: Tachometer used 60 years ago
          Series 6: The three sacred calculators
          Series 7: The first home computer
          Series 8: Sentimental journey to Nordkapp
          Series 9: Change of photograph
          Series 10: Story of passport

   
The others

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Brief Self Introduction
Mail address: PGA02322@nifty.com
Place of residence: Tokyo, Japan

Major Past Activities

Membership of Academic/Professional Societies

Curriculum Vitae

Recent Publications

The center of gravity of recent publications has been shifting from those with the topics in fluids engineering to those in engineering education. Please refer to Publications List of the recent papers written in English.